diff --git a/.gitignore b/.gitignore
index c29af83..dc4a252 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,52 @@
 .vscode
 __pycache__
-test_data
\ No newline at end of file
+test_data
+
+# Python
+*.py[cod]
+*$py.class
+*.so
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+
+# Virtual environments
+venv/
+ENV/
+env/
+
+# IDE
+.idea/
+*.swp
+*.swo
+
+# Environment variables
+.env
+.env.local
+
+# Test coverage
+.htmlcov/
+.coverage
+.coverage.*
+coverage.xml
+
+# Pytest
+.pytest_cache/
+
+# Generated files
+*.png
+*.csv
+data/
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..5aadacd
--- /dev/null
+++ b/README.md
@@ -0,0 +1,78 @@
+# Disk Checker
+
+Disk benchmarking and latency visualization tool for fio and badblocks output.
+
+## Features
+
+- Parse fio JSON+ latency CSV files
+- Generate histogram and CDF plots
+- REST API for remote benchmarking
+- Async job management for long-running benchmarks
+
+## Installation
+
+```bash
+git clone <repository>
+cd disk-checker
+python -m venv venv
+source venv/bin/activate
+pip install -e ".[dev]"
+```
+
+## CLI Usage
+
+```bash
+# Basic usage
+python -m disk_checker scan_latency.csv
+
+# With options
+python -m disk_checker scan_latency.csv --metric read_clat --unit ms --log-x
+
+# Generate CDF
+python -m disk_checker scan_latency.csv --cdf
+
+# View all metrics
+python -m disk_checker scan_latency.csv --all-metrics
+```
+
+## API Usage
+
+```bash
+# Start the server
+python -m disk_checker.scripts.serve --host 0.0.0.0 --port 8000
+
+# Access API docs at http://localhost:8000/docs
+```
+
+### API Endpoints
+
+- `POST /api/v1/scan` - Upload CSV and get analysis
+- `POST /api/v1/plot` - Generate and return plot image
+- `POST /api/v1/benchmark` - Start a benchmark job
+- `GET /api/v1/jobs/{id}` - Check job status
+- `GET /health` - Health check
+
+## Architecture
+
+```
+disk-checker/
+├── src/disk_checker/
+│   ├── core/          # Business logic (extractor, converter, helpers, orchestrator)
+│   ├── plotting/      # Visualization (matplotlib)
+│   ├── web/           # FastAPI backend
+│   └── scripts/       # Entry points (cli, serve)
+├── tests/             # Test suite
+└── data/              # Sample data
+```
+
+## Testing
+
+```bash
+pytest
+pytest --cov=disk_checker
+pytest --cov=disk_checker --cov-report=html
+```
+
+## License
+
+MIT
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..acb03f9
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,53 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "disk-checker"
+version = "0.1.0"
+description = "Disk benchmarking and latency visualization tool"
+readme = "README.md"
+requires-python = ">=3.10"
+dependencies = [
+    "pandas>=2.0",
+    "numpy>=1.24",
+    "matplotlib>=3.7",
+    "fastapi>=0.100",
+    "uvicorn[standard]>=0.23",
+    "python-multipart>=0.0.6",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=7.0",
+    "pytest-asyncio>=0.21",
+    "pytest-cov>=4.0",
+    "black>=23.0",
+    "ruff>=0.1.0",
+    "mypy>=1.0",
+]
+
+[project.scripts]
+disk-checker = "disk_checker.scripts.cli:main"
+disk-checker-serve = "disk_checker.scripts.serve:main"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/disk_checker"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+python_files = ["test_*.py"]
+python_functions = ["test_*"]
+
+[tool.black]
+line-length = 100
+target-version = ["py310"]
+
+[tool.ruff]
+line-length = 100
+target-version = "py310"
+
+[tool.mypy]
+python_version = "3.10"
+warn_return_any = true
+warn_unused_configs = true
\ No newline at end of file
diff --git a/src/disk_checker/__init__.py b/src/disk_checker/__init__.py
new file mode 100644
index 0000000..3b76229
--- /dev/null
+++ b/src/disk_checker/__init__.py
@@ -0,0 +1,3 @@
+"""Disk Checker - Disk benchmarking and latency visualization tool."""
+
+__version__ = "0.1.0"
\ No newline at end of file
diff --git a/src/disk_checker/__main__.py b/src/disk_checker/__main__.py
new file mode 100644
index 0000000..6e1b3a5
--- /dev/null
+++ b/src/disk_checker/__main__.py
@@ -0,0 +1,6 @@
+"""Allow running disk-checker as a module: python -m disk_checker"""
+
+from disk_checker.scripts.cli import main
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/src/disk_checker/core/__init__.py b/src/disk_checker/core/__init__.py
new file mode 100644
index 0000000..90ca7a2
--- /dev/null
+++ b/src/disk_checker/core/__init__.py
@@ -0,0 +1,14 @@
+"""Core business logic module."""
+
+from .extractor import load_latency_csv
+from .converter import to_unit, UNIT_FACTORS, UNIT_LABELS
+from .helpers import human_count, percentile_table
+
+__all__ = [
+    "load_latency_csv",
+    "to_unit",
+    "UNIT_FACTORS",
+    "UNIT_LABELS",
+    "human_count",
+    "percentile_table",
+]
\ No newline at end of file
diff --git a/src/disk_checker/core/converter.py b/src/disk_checker/core/converter.py
new file mode 100644
index 0000000..215e925
--- /dev/null
+++ b/src/disk_checker/core/converter.py
@@ -0,0 +1,32 @@
+"""Unit conversion utilities for latency data."""
+
+from typing import Dict
+import numpy as np
+
+UNIT_FACTORS: Dict[str, float] = {
+    "ns": 1.0,
+    "us": 1e3,
+    "ms": 1e6,
+    "s": 1e9,
+}
+
+UNIT_LABELS: Dict[str, str] = {
+    "ns": "ns",
+    "us": "µs",
+    "ms": "ms",
+    "s": "s",
+}
+
+
+def to_unit(values_ns, unit: str) -> np.ndarray:
+    """
+    Convert nanosecond values to the specified unit.
+
+    Args:
+        values_ns: Values in nanoseconds
+        unit: Target unit (ns, us, ms, s)
+
+    Returns:
+        Converted values as numpy array
+    """
+    return np.asarray(values_ns, dtype=float) / UNIT_FACTORS[unit]
\ No newline at end of file
diff --git a/src/disk_checker/core/drive_scanner.py b/src/disk_checker/core/drive_scanner.py
new file mode 100644
index 0000000..27d217e
--- /dev/null
+++ b/src/disk_checker/core/drive_scanner.py
@@ -0,0 +1,130 @@
+"""Drive detection module for disk-checker."""
+
+import json
+import subprocess
+from typing import Dict, List
+from dataclasses import dataclass
+from pathlib import Path
+
+
+@dataclass
+class DriveInfo:
+    """Information about a block device."""
+    name: str           # e.g., "sda", "sdb"
+    path: str           # e.g., "/dev/sda"
+    size: str           # e.g., "232.9G"
+    model: str          # e.g., "CT250MX500SSD1"
+    type: str           # e.g., "disk", "part"
+    mounted: bool       # True if currently mounted
+    mount_point: str = ""  # e.g., "/", "/home"
+    serial: str = ""    # e.g., "2131G5F25137"
+
+
+def get_mounted_devices() -> set:
+    """
+    Get set of mounted device paths.
+    
+    Returns:
+        Set of device paths that are currently mounted
+    """
+    mounted = set()
+    
+    # Method 1: Parse lsblk with mount points
+    try:
+        result = subprocess.run(
+            ["lsblk", "-J", "-o", "NAME,MOUNTPOINT"],
+            capture_output=True,
+            text=True,
+            check=True
+        )
+        data = json.loads(result.stdout)
+        for device in data.get("blockdevices", []):
+            mountpoint = device.get("mountpoint")
+            if mountpoint:
+                # Add both full path and device name
+                mounted.add(f"/dev/{device['name']}")
+                mounted.add(device["name"])
+    except (subprocess.CalledProcessError, json.JSONDecodeError):
+        print("lsblk failed to retrieve mounted devices information")
+        pass
+    
+    # Method 2: Parse /proc/mounts
+    try:
+        with open("/proc/mounts", "r") as f:
+            for line in f:
+                parts = line.split()
+                if len(parts) >= 2 and parts[0].startswith("/dev/"):
+                    mounted.add(parts[0])
+                    # Also add device name without /dev/
+                    mounted.add(parts[0].replace("/dev/", ""))
+    except (FileNotFoundError, IOError):
+        print("/proc/mounts failed to retrieve mounted devices information")
+        pass
+    
+    return mounted
+
+
+def scan_drives() -> List[DriveInfo]:
+    """
+    Scan host system for available block devices.
+    
+    Returns:
+        List of DriveInfo objects for physical disks
+    """
+    mounted_devices = get_mounted_devices()
+    drives = []
+    
+    try:
+        # Get block devices with lsblk
+        result = subprocess.run(
+            [
+                "lsblk",
+                "-J",           # JSON output
+                "-d",           # Only disks (not partitions)
+                "-b",           # Show size in bytes
+                "-o", "NAME,SIZE,TYPE,MODEL,Serial,MOUNTPOINT"
+            ],
+            capture_output=True,
+            text=True,
+            check=True
+        )
+        
+        data = json.loads(result.stdout)
+        
+        for device in data.get("blockdevices", []):
+            # Only include physical disks
+            if device.get("type") != "disk":
+                continue
+            
+            name = device.get("name", "")
+            path = f"/dev/{name}"
+            
+            # Check if mounted
+            is_mounted = False
+            #is_mounted = path in mounted_devices or name in mounted_devices
+            for md in mounted_devices:
+                is_mounted |= path in md
+            
+            drive = DriveInfo(
+                name=name,
+                path=path,
+                size=device.get("size", "Unknown"),
+                model=device.get("model") or "",
+                type="disk",
+                mounted=is_mounted,
+                mount_point=device.get("mountpoint", ""),
+                serial=device.get("serial") or ""
+            )
+            drives.append(drive)
+            
+    except subprocess.CalledProcessError as e:
+        # If lsblk fails, return empty list
+        print("lsblk failed to parse drives data")
+        print(e)
+        pass
+    except json.JSONDecodeError as e:
+        print("json decoder error")
+        print(e)
+        pass
+    
+    return drives
\ No newline at end of file
diff --git a/src/disk_checker/core/extractor.py b/src/disk_checker/core/extractor.py
new file mode 100644
index 0000000..4b80e50
--- /dev/null
+++ b/src/disk_checker/core/extractor.py
@@ -0,0 +1,88 @@
+"""CSV data extraction module for fio latency data."""
+
+from pathlib import Path
+import pandas as pd
+from typing import Optional
+
+
+def load_latency_csv(path: str) -> pd.DataFrame:
+    """
+    Parse wide-format fio JSON+ CSV into long-format DataFrame.
+
+    Transforms wide-format columns (e.g., read_clat_ns_count) into rows with
+    a metric identifier, making it easier to group and analyze by operation type.
+
+    Args:
+        path: Path to CSV file generated by fio_jsonplus_clat2csv
+
+    Returns:
+        DataFrame with columns: metric, latency_ns, count, cumulative, percentile
+
+    Raises:
+        ValueError: If CSV format is invalid or contains no valid data
+    """
+    df = pd.read_csv(path, skipinitialspace=True)
+    df.columns = [str(c).strip() for c in df.columns]
+
+    # Drop trailing unnamed / empty columns
+    df = df.loc[:, ~df.columns.str.match(r"^Unnamed")]
+    df = df.loc[:, df.columns != ""]
+
+    nsec_col = df.columns[0]
+    if "nsec" not in nsec_col.lower():
+        raise ValueError(
+            f"expected first column to be 'nsec', got {nsec_col!r}"
+        )
+
+    # Coerce the nsec column to numeric
+    df[nsec_col] = pd.to_numeric(df[nsec_col], errors="coerce")
+    df = df.dropna(subset=[nsec_col])
+
+    # Discover metric triples: <metric>_count / _cumulative / _percentile
+    metrics = {}
+    for col in df.columns:
+        if col == nsec_col:
+            continue
+        for suffix in ("_count", "_cumulative", "_percentile"):
+            if col.endswith(suffix):
+                base = col[: -len(suffix)]
+                metrics.setdefault(base, {})[suffix[1:]] = col
+
+    if not metrics:
+        raise ValueError("no *_count columns found in CSV")
+
+    frames = []
+    for base, cols in metrics.items():
+        count_col = cols["count"]
+
+        # Coerce count to numeric
+        counts = pd.to_numeric(df[count_col], errors="coerce")
+
+        # Keep only rows where the count column actually has a number
+        mask = counts.notna()
+        if not mask.any():
+            continue
+
+        sub = pd.DataFrame({
+            "latency_ns": df.loc[mask, nsec_col].values,
+            "count": counts[mask].astype(int).values,
+        })
+        if "cumulative" in cols:
+            sub["cumulative"] = pd.to_numeric(
+                df.loc[mask, cols["cumulative"]], errors="coerce"
+            ).values
+        if "percentile" in cols:
+            sub["percentile"] = pd.to_numeric(
+                df.loc[mask, cols["percentile"]], errors="coerce"
+            ).values
+
+        # read_clat_ns -> read_clat
+        sub["metric"] = base.replace("_ns", "")
+        frames.append(sub)
+
+    if not frames:
+        raise ValueError("no metric had any numeric count data")
+
+    out = pd.concat(frames, ignore_index=True)
+    out = out[out["count"] > 0].reset_index(drop=True)
+    return out
\ No newline at end of file
diff --git a/src/disk_checker/core/helpers.py b/src/disk_checker/core/helpers.py
new file mode 100644
index 0000000..e6d3f4d
--- /dev/null
+++ b/src/disk_checker/core/helpers.py
@@ -0,0 +1,62 @@
+"""Helper functions for formatting and display."""
+
+from typing import List
+import numpy as np
+import pandas as pd
+from matplotlib.ticker import FuncFormatter
+
+from .converter import to_unit, UNIT_LABELS
+
+
+def human_count(x, _pos=None) -> str:
+    """
+    Format large numbers with K/M/G suffixes for axis labels.
+
+    Args:
+        x: Numeric value to format
+        _pos: Matplotlib tick position (unused)
+
+    Returns:
+        Formatted string (e.g., "1.5M", "3.2G")
+    """
+    if x >= 1e9:
+        return f"{x/1e9:.1f}G"
+    if x >= 1e6:
+        return f"{x/1e6:.1f}M"
+    if x >= 1e3:
+        return f"{x/1e3:.0f}k"
+    return f"{x:.0f}"
+
+
+def percentile_table(df: pd.DataFrame, metric: str, unit: str, pcts: List[float]) -> str:
+    """
+    Generate a formatted table showing latency values at specified percentiles.
+
+    Args:
+        df: Long-format DataFrame from load_latency_csv
+        metric: Metric name (e.g., 'read_clat')
+        unit: Display unit (ns, us, ms, s)
+        pcts: List of percentile values (e.g., [50, 90, 99])
+
+    Returns:
+        Formatted string table
+    """
+    g = df[df["metric"] == metric].sort_values("latency_ns")
+    if g.empty:
+        return f"(no data for metric {metric})"
+
+    counts = g["count"].values.astype(float)
+    total = int(counts.sum())
+    cdf = np.cumsum(counts) / total * 100.0
+    lat = to_unit(g["latency_ns"].values, unit)
+
+    lines = [
+        f"\nMetric: {metric}   (total I/Os: {total:,})",
+        f"  {'percentile':>12}  {'latency':>14}",
+    ]
+
+    for p in pcts:
+        idx = min(np.searchsorted(cdf, p), len(lat) - 1)
+        lines.append(f"  {p:>11.2f}%  {lat[idx]:>12.3f} {UNIT_LABELS[unit]}")
+
+    return "\n".join(lines)
\ No newline at end of file
diff --git a/src/disk_checker/core/orchestrator.py b/src/disk_checker/core/orchestrator.py
new file mode 100644
index 0000000..656385b
--- /dev/null
+++ b/src/disk_checker/core/orchestrator.py
@@ -0,0 +1,164 @@
+"""Tool orchestration module for running disk benchmarks."""
+
+import asyncio
+import subprocess
+from dataclasses import dataclass, field
+from enum import Enum
+from pathlib import Path
+from typing import Dict, Optional
+
+
+class ToolStatus(Enum):
+    """Status of a benchmark job."""
+    PENDING = "pending"
+    RUNNING = "running"
+    COMPLETED = "completed"
+    FAILED = "failed"
+
+
+@dataclass
+class JobResult:
+    """Result of a benchmark job."""
+    job_id: str
+    status: ToolStatus
+    output_path: Optional[Path] = None
+    error: Optional[str] = None
+    metadata: Dict = field(default_factory=dict)
+
+
+class Orchestrator:
+    """
+    Orchestrates disk benchmarking tools (fio, badblocks, etc.)
+
+    Provides async interfaces for running benchmarks and collecting results.
+    """
+
+    def __init__(self, work_dir: Path = Path(".")):
+        self.work_dir = work_dir
+        self._jobs: Dict[str, JobResult] = {}
+
+    async def run_fio(
+        self,
+        device: str,
+        job_file: Optional[Path] = None,
+        output_format: str = "jsonplus",
+        **kwargs,
+    ) -> Path:
+        """
+        Run fio benchmark and return path to output file.
+
+        Args:
+            device: Block device path (e.g., '/dev/sda')
+            job_file: Optional fio job file
+            output_format: Output format (json, jsonplus, csv)
+            **kwargs: Additional fio options
+
+        Returns:
+            Path to output file
+
+        Raises:
+            subprocess.CalledProcessError: If fio command fails
+        """
+        job_id = f"fio_{asyncio.get_event_loop().time()}"
+        output_path = self.work_dir / f"{job_id}.{output_format}"
+
+        cmd = ["fio", "--output-format=jsonplus"]
+        if job_file:
+            cmd.extend(["--filename", str(device)])
+        else:
+            cmd.extend(["--name=test", "--rw=randread", "--bs=4k"])
+
+        cmd.extend(["--output", str(output_path)])
+        cmd.extend([f"--output-format={output_format}"])
+
+        for k, v in kwargs.items():
+            cmd.extend([f"--{k}={v}"])
+
+        self._jobs[job_id] = JobResult(
+            job_id=job_id,
+            status=ToolStatus.RUNNING,
+            output_path=output_path,
+        )
+
+        try:
+            await asyncio.create_subprocess_exec(
+                *cmd,
+                stdout=asyncio.subprocess.PIPE,
+                stderr=asyncio.subprocess.PIPE,
+            )
+            self._jobs[job_id] = JobResult(
+                job_id=job_id,
+                status=ToolStatus.COMPLETED,
+                output_path=output_path,
+            )
+            return output_path
+        except subprocess.CalledProcessError as e:
+            self._jobs[job_id] = JobResult(
+                job_id=job_id,
+                status=ToolStatus.FAILED,
+                error=str(e),
+            )
+            raise
+
+    async def run_badblocks(
+        self,
+        device: str,
+        blocks_count: Optional[int] = None,
+        **kwargs,
+    ) -> Path:
+        """
+        Run badblocks scan on device.
+
+        Args:
+            device: Block device path
+            blocks_count: Number of blocks to scan
+            **kwargs: Additional badblocks options
+
+        Returns:
+            Path to badblocks output file
+        """
+        job_id = f"badblocks_{asyncio.get_event_loop().time()}"
+        output_path = self.work_dir / f"{job_id}.txt"
+
+        cmd = ["badblocks", "-w", "-s", "-p", "0", "-t", "RANDOM", "-o"]
+        cmd.extend([str(output_path), str(device)])
+
+        if blocks_count:
+            cmd.extend(["-b", str(blocks_count)])
+
+        for k, v in kwargs.items():
+            cmd.extend([f"-{k}", str(v)])
+
+        self._jobs[job_id] = JobResult(
+            job_id=job_id,
+            status=ToolStatus.RUNNING,
+            output_path=output_path,
+        )
+
+        try:
+            await asyncio.create_subprocess_exec(
+                *cmd,
+                stdout=asyncio.subprocess.PIPE,
+                stderr=asyncio.subprocess.PIPE,
+            )
+            self._jobs[job_id] = JobResult(
+                job_id=job_id,
+                status=ToolStatus.COMPLETED,
+                output_path=output_path,
+            )
+            return output_path
+        except subprocess.CalledProcessError as e:
+            self._jobs[job_id] = JobResult(
+                job_id=job_id,
+                status=ToolStatus.FAILED,
+                error=str(e),
+            )
+            raise
+
+    def get_job_status(self, job_id: str) -> Optional[JobResult]:
+        """Get status of a submitted job."""
+        return self._jobs.get(job_id)
+
+    def list_jobs(self) -> Dict[str, JobResult]:
+        """List all jobs."""
+        return self._jobs.copy()
\ No newline at end of file
diff --git a/src/disk_checker/core/tool_scanner.py b/src/disk_checker/core/tool_scanner.py
new file mode 100644
index 0000000..ae0875f
--- /dev/null
+++ b/src/disk_checker/core/tool_scanner.py
@@ -0,0 +1,57 @@
+"""Tool detection module for disk-checker."""
+
+import shutil
+from typing import Dict, List
+from dataclasses import dataclass
+
+
+@dataclass
+class ToolInfo:
+    """Information about a benchmarking tool."""
+    name: str
+    available: bool
+    version: str = ""
+
+
+# Tools to scan for
+TOOLS_TO_SCAN = [
+    "fio",
+    "badblocks",
+    "smartctl",
+    "iozone",
+    "hdparm",
+]
+
+
+def scan_tools() -> Dict[str, ToolInfo]:
+    """
+    Scan host system for available benchmarking tools.
+    
+    Returns:
+        Dictionary mapping tool names to ToolInfo objects
+    """
+    results = {}
+    for tool_name in TOOLS_TO_SCAN:
+        available = shutil.which(tool_name) is not None
+        version = ""
+        if available:
+            # Try to get version (optional enhancement)
+            try:
+                import subprocess
+                result = subprocess.run(
+                    [tool_name, "--version"],
+                    capture_output=True,
+                    text=True,
+                    timeout=2
+                )
+                version = result.stdout.split("\n")[0][:50]
+            except Exception:
+                # If we can't even run '--version', then 
+                # a tool is not considered as available
+                available = False
+        results[tool_name] = ToolInfo(
+            name=tool_name,
+            available=available,
+            version=version
+        )
+    return results
\ No newline at end of file
diff --git a/src/disk_checker/plotting/__init__.py b/src/disk_checker/plotting/__init__.py
new file mode 100644
index 0000000..0718ebf
--- /dev/null
+++ b/src/disk_checker/plotting/__init__.py
@@ -0,0 +1,5 @@
+"""Plotting module for disk latency visualization."""
+
+from .plots import draw_histogram, draw_cdf, generate_plot
+
+__all__ = ["draw_histogram", "draw_cdf", "generate_plot"]
\ No newline at end of file
diff --git a/src/disk_checker/plotting/plots.py b/src/disk_checker/plotting/plots.py
new file mode 100644
index 0000000..270eefc
--- /dev/null
+++ b/src/disk_checker/plotting/plots.py
@@ -0,0 +1,162 @@
+"""Plotting module for disk latency visualization."""
+
+import matplotlib
+matplotlib.use("Agg")  # Non-interactive backend for server environments
+import matplotlib.pyplot as plt
+from matplotlib.ticker import FuncFormatter
+import numpy as np
+from pathlib import Path
+from typing import List, Optional
+
+from disk_checker.core.converter import to_unit, UNIT_LABELS
+from disk_checker.core.helpers import human_count
+
+
+def draw_histogram(
+    ax,
+    df,
+    metrics: List[str],
+    unit: str = "us",
+    log_y: bool = False,
+    log_x: bool = False,
+    normalize: bool = False,
+) -> None:
+    """
+    Draw a histogram showing the distribution of latencies for each metric.
+
+    Uses a step plot (where="post") to show the discrete nature of the data.
+    If normalize=True, Y-axis shows probability density instead of counts.
+
+    Args:
+        ax: Matplotlib axis object
+        df: Long-format DataFrame from load_latency_csv
+        metrics: List of metric names to plot
+        unit: X-axis unit (ns, us, ms, s)
+        log_y: Use logarithmic Y scale
+        log_x: Use logarithmic X scale
+        normalize: Normalize to probability density
+    """
+    for metric in metrics:
+        g = df[df["metric"] == metric].sort_values("latency_ns")
+        if g.empty:
+            continue
+
+        x = to_unit(g["latency_ns"].values, unit)
+        y = g["count"].values.astype(float)
+
+        if normalize:
+            s = y.sum()
+            if s > 0:
+                y = y / s
+
+        ax.step(x, y, where="post", lw=1.4, label=metric)
+        ax.fill_between(x, y, step="post", alpha=0.25)
+
+    ax.set_xlabel(f"Latency ({UNIT_LABELS[unit]})")
+    ax.set_ylabel("Probability" if normalize else "Number of I/Os")
+    ax.set_title("Completion latency distribution")
+    ax.grid(True, which="both", ls=":", alpha=0.5)
+
+    if not normalize:
+        ax.yaxis.set_major_formatter(FuncFormatter(human_count))
+    if log_y:
+        ax.set_yscale("log")
+    if log_x:
+        ax.set_xscale("log")
+    if len(metrics) > 1:
+        ax.legend(title="metric", fontsize=9)
+
+
+def draw_cdf(ax, df, metrics: List[str], unit: str = "us", log_x: bool = False) -> None:
+    """
+    Draw a Cumulative Distribution Function (CDF).
+
+    Shows the percentage of I/Os completed within each latency threshold.
+    Each metric gets its own line; Y-axis ranges from 0% to 100%.
+
+    Args:
+        ax: Matplotlib axis object
+        df: Long-format DataFrame
+        metrics: List of metric names
+        unit: X-axis unit
+        log_x: Use logarithmic X scale
+    """
+    for metric in metrics:
+        g = df[df["metric"] == metric].sort_values("latency_ns")
+        if g.empty:
+            continue
+
+        x = to_unit(g["latency_ns"].values, unit)
+        counts = g["count"].values.astype(float)
+        total = counts.sum()
+        if total <= 0:
+            continue
+
+        cdf = np.cumsum(counts) / total * 100.0
+        ax.plot(x, cdf, lw=1.6, label=f"{metric} (n={int(total):,})")
+
+    ax.set_xlabel(f"Latency ({UNIT_LABELS[unit]})")
+    ax.set_ylabel("Cumulative % of I/Os")
+    ax.set_title("Cumulative latency distribution")
+    ax.set_ylim(0, 100)
+    ax.grid(True, which="both", ls=":", alpha=0.5)
+    ax.yaxis.set_major_formatter(FuncFormatter(lambda v, _: f"{v:.0f}%"))
+
+    if log_x:
+        ax.set_xscale("log")
+    ax.legend(fontsize=9)
+
+
+def generate_plot(
+    df,
+    metrics: List[str],
+    output_path: Path,
+    unit: str = "us",
+    log_y: bool = False,
+    log_x: bool = False,
+    normalize: bool = False,
+    show_cdf: bool = False,
+    cdf_only: bool = False,
+    title: str = "",
+    dpi: int = 150,
+) -> Path:
+    """
+    Generate a complete plot with histogram and/or CDF.
+
+    Creates the appropriate subplot layout based on the options provided.
+
+    Args:
+        df: Long-format DataFrame
+        metrics: Metrics to plot
+        output_path: Where to save the plot
+        unit: X-axis unit
+        log_y: Logarithmic Y scale
+        log_x: Logarithmic X scale
+        normalize: Normalize histogram
+        show_cdf: Show CDF below histogram
+        cdf_only: Show only CDF
+        title: Plot title
+        dpi: Output resolution
+
+    Returns:
+        Path to saved plot
+    """
+    if cdf_only:
+        fig, ax = plt.subplots(figsize=(11, 6))
+        draw_cdf(ax, df, metrics, unit, log_x)
+    elif show_cdf:
+        fig, (ax1, ax2) = plt.subplots(2, 1, figsize=(11, 10))
+        draw_histogram(
+            ax1, df, metrics, unit, log_y, log_x, normalize
+        )
+        draw_cdf(ax2, df, metrics, unit, log_x)
+    else:
+        fig, ax = plt.subplots(figsize=(11, 6))
+        draw_histogram(ax, df, metrics, unit, log_y, log_x, normalize)
+
+    if title:
+        fig.suptitle(title, fontsize=13, y=0.995)
+    fig.tight_layout()
+    fig.savefig(output_path, dpi=dpi, bbox_inches="tight")
+    plt.close(fig)
+    return output_path
\ No newline at end of file
diff --git a/src/disk_checker/scripts/__init__.py b/src/disk_checker/scripts/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/disk_checker/scripts/cli.py b/src/disk_checker/scripts/cli.py
new file mode 100644
index 0000000..0b713f7
--- /dev/null
+++ b/src/disk_checker/scripts/cli.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+"""
+CLI entry point for disk-checker.
+
+Usage:
+    python -m disk_checker scan_latency.csv
+    disk-checker scan_latency.csv --metric read_clat --unit ms
+"""
+
+import argparse
+import sys
+from pathlib import Path
+
+from disk_checker.core.extractor import load_latency_csv
+from disk_checker.core.helpers import percentile_table
+from disk_checker.plotting.plots import generate_plot
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Plot fio json+ wide-format latency CSV."
+    )
+    parser.add_argument("csv", help="CSV from fio_jsonplus_clat2csv")
+    parser.add_argument("--metric", default=None,
+                       help="Metric to plot (e.g. read_clat). "
+                            "If omitted, the metric with the most I/Os is used.")
+    parser.add_argument("--all-metrics", action="store_true",
+                       help="Plot every metric that has data")
+    parser.add_argument("--unit", choices=["ns", "us", "ms", "s"], default="us",
+                       help="X-axis latency unit (default: us)")
+    parser.add_argument("--log-y", action="store_true")
+    parser.add_argument("--log-x", action="store_true")
+    parser.add_argument("--cdf", action="store_true",
+                       help="Add a CDF subplot below the histogram")
+    parser.add_argument("--cdf-only", action="store_true")
+    parser.add_argument("--normalize", action="store_true",
+                       help="Normalize histogram to a probability density")
+    parser.add_argument("--percentiles", default="50,90,99,99.9,99.99")
+    parser.add_argument("--no-percentiles", action="store_true")
+    parser.add_argument("--output", "-o", default=None)
+    parser.add_argument("--dpi", type=int, default=150)
+    parser.add_argument("--title", default="")
+    parser.add_argument("--show", action="store_true")
+    args = parser.parse_args()
+
+    if not Path(args.csv).is_file():
+        sys.exit(f"error: file not found: {args.csv}")
+
+    df = load_latency_csv(args.csv)
+    if df.empty:
+        sys.exit("error: no latency data in CSV")
+
+    available = sorted(df["metric"].unique())
+    print("Metrics with data:", ", ".join(available))
+
+    if args.all_metrics:
+        metrics = available
+    elif args.metric:
+        if args.metric not in available:
+            sys.exit(f"error: metric {args.metric!r} not in {available}")
+        metrics = [args.metric]
+    else:
+        totals = df.groupby("metric")["count"].sum().sort_values(ascending=False)
+        metrics = [totals.index[0]]
+        print(f"Auto-selected metric: {metrics[0]}")
+
+    output = args.output or f"{Path(args.csv).stem}_latency.png"
+    generate_plot(
+        df=df,
+        metrics=metrics,
+        output_path=Path(output),
+        unit=args.unit,
+        log_y=args.log_y,
+        log_x=args.log_x,
+        normalize=args.normalize,
+        show_cdf=args.cdf,
+        cdf_only=args.cdf_only,
+        title=args.title,
+        dpi=args.dpi,
+    )
+    print(f"Saved plot to {output}")
+
+    if not args.no_percentiles:
+        try:
+            pcts = [float(x) for x in args.percentiles.split(",") if x.strip()]
+        except ValueError:
+            sys.exit("error: --percentiles must be comma-separated numbers")
+        for m in metrics:
+            print(percentile_table(df, m, args.unit, pcts))
+
+    if args.show:
+        import matplotlib.pyplot as plt
+        plt.show()
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/src/disk_checker/scripts/serve.py b/src/disk_checker/scripts/serve.py
new file mode 100644
index 0000000..a977dc0
--- /dev/null
+++ b/src/disk_checker/scripts/serve.py
@@ -0,0 +1,32 @@
+"""Startup script for the web server."""
+
+import argparse
+import uvicorn
+from pathlib import Path
+
+
+def main():
+    """Main entry point for the web server."""
+    parser = argparse.ArgumentParser(description="Start Disk Checker API server")
+    parser.add_argument("--host", default="127.0.0.1", help="Host to bind to")
+    parser.add_argument("--port", type=int, default=8000, help="Port to bind to")
+    parser.add_argument("--workers", type=int, default=1, help="Number of workers")
+    parser.add_argument("--reload", action="store_true", help="Enable auto-reload")
+    parser.add_argument("--work-dir", type=Path, default=Path("."), help="Work directory")
+    args = parser.parse_args()
+
+    # Set work directory in environment
+    import os
+    os.environ["DISK_CHECKER_WORK_DIR"] = str(args.work_dir)
+
+    uvicorn.run(
+        "disk_checker.web.server:app",
+        host=args.host,
+        port=args.port,
+        workers=args.workers,
+        reload=args.reload,
+    )
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/src/disk_checker/web/__init__.py b/src/disk_checker/web/__init__.py
new file mode 100644
index 0000000..3753ac5
--- /dev/null
+++ b/src/disk_checker/web/__init__.py
@@ -0,0 +1,6 @@
+"""Web backend module for disk-checker API."""
+
+from .web_routes import web_router
+from .routes import api_router
+
+__all__ = ["web_router", "api_router"]
\ No newline at end of file
diff --git a/src/disk_checker/web/models.py b/src/disk_checker/web/models.py
new file mode 100644
index 0000000..adb9621
--- /dev/null
+++ b/src/disk_checker/web/models.py
@@ -0,0 +1,52 @@
+"""Pydantic models for the web API."""
+
+from pydantic import BaseModel, Field
+from typing import List, Optional, Dict, Any
+from enum import Enum
+
+
+class ToolType(str, Enum):
+    """Available benchmarking tools."""
+    FIO = "fio"
+    BADBLOCKS = "badblocks"
+    IO_URING = "io_uring"
+
+
+class JobStatus(str, Enum):
+    """Status of a benchmark job."""
+    PENDING = "pending"
+    RUNNING = "running"
+    COMPLETED = "completed"
+    FAILED = "failed"
+
+
+class BenchmarkRequest(BaseModel):
+    """Request to start a benchmark job."""
+    device: str = Field(..., description="Block device path (e.g., /dev/sda)")
+    tool: ToolType = ToolType.FIO
+    job_file: Optional[str] = None
+    options: Dict[str, Any] = Field(default_factory=dict)
+
+    class Config:
+        json_schema_extra = {
+            "example": {
+                "device": "/dev/sda",
+                "tool": "fio",
+                "options": {
+                    "rw": "randread",
+                    "bs": "4k",
+                    "size": "1G",
+                    "runtime": "60"
+                }
+            }
+        }
+
+
+class JobStatusResponse(BaseModel):
+    """Response with job status."""
+    job_id: str
+    status: JobStatus
+    output_path: Optional[str] = None
+    error: Optional[str] = None
+    created_at: Optional[str] = None
+    completed_at: Optional[str] = None
\ No newline at end of file
diff --git a/src/disk_checker/web/routes.py b/src/disk_checker/web/routes.py
new file mode 100644
index 0000000..3f1a0b7
--- /dev/null
+++ b/src/disk_checker/web/routes.py
@@ -0,0 +1,45 @@
+"""API routes for disk-checker web backend."""
+
+from fastapi import APIRouter, Request
+
+from disk_checker.core.tool_scanner import ToolInfo
+from disk_checker.core.drive_scanner import DriveInfo, scan_drives
+
+api_router = APIRouter()
+
+@api_router.get("/tools")
+async def get_available_tools(request: Request):
+    """
+    Get list of available benchmarking tools.
+    """
+    tools = request.app.state.available_tools
+    return {
+        tool_name: {
+            "name" : tool.name,
+            "available": tool.available,
+            "version" : tool.version
+        }
+        for tool_name, tool in tools.items()
+    }
+
+@api_router.get("/drives")
+async def get_available_drives(request: Request):
+    """
+    Get list of available block devices
+    Mounted drives are marked as unavailable
+    """
+    drives = scan_drives()
+    return {
+        "drives": [
+            {
+                "name": drive.name,
+                "path": drive.path,
+                "size": drive.size,
+                "model": drive.model,
+                "mounted": drive.mounted,
+                "mount_point": drive.mount_point,
+                "serial": drive.serial
+            }
+            for drive in drives
+        ]
+    }
\ No newline at end of file
diff --git a/src/disk_checker/web/server.py b/src/disk_checker/web/server.py
new file mode 100644
index 0000000..fedc834
--- /dev/null
+++ b/src/disk_checker/web/server.py
@@ -0,0 +1,80 @@
+"""FastAPI application for disk-checker web API."""
+
+import asyncio
+
+from pathlib import Path
+
+from fastapi import FastAPI
+from fastapi.staticfiles import StaticFiles
+from fastapi.templating import Jinja2Templates
+from fastapi.middleware.cors import CORSMiddleware
+from contextlib import asynccontextmanager
+import logging
+
+from disk_checker.core.orchestrator import Orchestrator
+from disk_checker.core.tool_scanner import scan_tools
+# Import and include routers
+from disk_checker.web.routes import api_router
+from disk_checker.web.web_routes import web_router
+
+
+# Get application root
+BASE_DIR = Path(__file__).resolve().parent.parent.parent.parent
+TEMPLATES_DIR = BASE_DIR / "templates"
+STATIC_DIR = BASE_DIR / "static"
+
+# Setup templates
+templates = Jinja2Templates(directory=str(TEMPLATES_DIR))
+
+# Setup logger
+logger = logging.getLogger(__name__)
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """Application lifespan handler."""
+    # Startup: initialize orchestrator
+    #app.state.orchestrator = Orchestrator(work_dir=app.state.work_dir)
+    app.state.jobs = {}
+
+    # Scan for available benchmarking tools
+    app.state.available_tools = await asyncio.to_thread(scan_tools)
+    logger.info(f"Available tools: {list(app.state.available_tools.keys())}")
+
+    # Store templates and static_dir path in app.state
+    app.state.templates = templates
+    app.state.static_dir = STATIC_DIR
+
+    logger.info("Disk Checker API started")
+    
+    yield
+    # Shutdown: cleanup
+    logger.info("Disk Checker API stopped")
+
+
+app = FastAPI(
+    title="Disk Checker API",
+    description="API for disk benchmarking and latency visualization",
+    version="0.1.0",
+    lifespan=lifespan,
+)
+# Setup static files
+app.mount("/static", StaticFiles(directory=str(STATIC_DIR)), name="static")
+# Include routers
+app.include_router(api_router, prefix="/api/v1")
+app.include_router(web_router)
+
+# Add CORS (permissive by default)
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Simple health endpoint
+@app.get("/health")
+async def health_check():
+    """Health check endpoint."""
+    return {"status": "ok", "version": "0.1.0"}
\ No newline at end of file
diff --git a/src/disk_checker/web/web_routes.py b/src/disk_checker/web/web_routes.py
new file mode 100644
index 0000000..7ed22cc
--- /dev/null
+++ b/src/disk_checker/web/web_routes.py
@@ -0,0 +1,65 @@
+from fastapi import APIRouter, Request
+from fastapi.templating import Jinja2Templates
+from typing import Dict
+
+web_router = APIRouter()
+
+# Navigation configuration - NEW TABS GO HERE!
+NAVIGATION = [
+    {"name": "home", "label": "Home", "url": "/", "icon": "bi-house"},
+    {"name": "benchmark", "label": "Benchmark", "url": "/benchmark", "icon": "bi-hdd"},
+    {"name": "jobs", "label": "Job Queue", "url": "/jobs", "icon": "bi-list-task"},
+]
+
+def get_active_tab(url: str) -> str:
+    """Determine which navigation tab is active."""
+    for nav_item in NAVIGATION:
+        if nav_item["url"] == url:
+            return nav_item["name"]
+    return "home"
+
+
+@web_router.get("/")
+async def render_home(request: Request):
+    """
+    Render the main page
+    """
+    tools = request.app.state.available_tools
+    return request.app.state.templates.TemplateResponse(
+        name="index.html",
+        request=request,
+        context={
+            "tools":tools,
+            "navigation": NAVIGATION,
+            "active_tab": get_active_tab("/")
+        }
+    )
+
+@web_router.get("/benchmark")
+async def render_benchmark(request: Request):
+    """Render the benchmark page."""
+    templates: Jinja2Templates = request.app.state.templates
+    
+    return templates.TemplateResponse(
+        name="benchmark.html",
+        request=request,
+        context={
+            "navigation": NAVIGATION,
+            "active_tab": get_active_tab("/benchmark")
+        }
+    )
+
+
+@web_router.get("/jobs")
+async def render_jobs(request: Request):
+    """Render the job queue page."""
+    templates: Jinja2Templates = request.app.state.templates
+    
+    return templates.TemplateResponse(
+        name="jobs.html",
+        request=request,
+        context={
+            "navigation": NAVIGATION,
+            "active_tab": get_active_tab("/jobs")
+        }
+    )
\ No newline at end of file
diff --git a/static/css/style.css b/static/css/style.css
new file mode 100644
index 0000000..43426f3
--- /dev/null
+++ b/static/css/style.css
@@ -0,0 +1,70 @@
+/* Basic styling for Disk Checker */
+.container {
+    max-width: 1200px;
+}
+
+.card {
+    transition: transform 0.2s;
+}
+
+.card:hover {
+    transform: translateY(-2px);
+    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
+}
+
+.badge {
+    font-size: 0.9rem;
+}
+
+/* Drive selector cards */
+.drive-selector-card {
+    transition: all 0.2s ease;
+}
+
+.drive-selector-card .btn-check:checked + .btn {
+    background-color: #e7f1ff;
+    border-color: #0d6efd;
+    box-shadow: 0 0 0 0.2rem rgba(13, 110, 253, 0.25);
+}
+
+.drive-selector-card .btn {
+    border-radius: 0.5rem;
+    padding: 1rem;
+}
+
+.drive-selector-card .btn:hover {
+    background-color: #f8f9fa;
+}
+
+.drive-selector-card .btn-check:checked + .btn:hover {
+    background-color: #e7f1ff;
+}
+
+/* General drive cards */
+.drive-card {
+    transition: all 0.3s ease;
+    height: 100%;
+}
+
+.drive-card.available {
+    border-left: 4px solid #28a745;
+}
+
+.drive-card.disabled {
+    border-left: 4px solid #6c757d;
+    opacity: 0.7;
+}
+
+.drive-card:hover:not(.disabled) {
+    transform: translateY(-2px);
+    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
+}
+
+/* Make disabled cards look unavailable */
+.drive-card.disabled .card-title {
+    color: #6c757d;
+}
+
+.drive-card.disabled .card-text {
+    color: #6c757d;
+}
\ No newline at end of file
diff --git a/static/js/main.js b/static/js/main.js
new file mode 100644
index 0000000..f88e68f
--- /dev/null
+++ b/static/js/main.js
@@ -0,0 +1,165 @@
+/**
+ * Disk Checker - Main JavaScript
+ * Handles HTMX events and dynamic content rendering
+ */
+
+// Global state
+let selectedDrive = null;
+
+// Render drives after HTMX loads them
+function renderDrives(data) {
+    const container = document.getElementById('drives-content');
+    if (!container) return;
+    
+    container.innerHTML = '';
+
+    if (!data.drives || data.drives.length === 0) {
+        container.innerHTML = '<div class="col-12"><p class="text-muted">No drives found.</p></div>';
+        return;
+    }
+
+    data.drives.forEach(drive => {
+        const col = document.createElement('div');
+        col.className = 'col-md-4 mb-3';
+
+        const card = document.createElement('div');
+        card.className = `drive-card ${drive.mounted ? 'disabled' : 'available'}`;
+
+        card.innerHTML = `
+            <div class="card-body">
+                <h5 class="card-title">${drive.name}</h5>
+                <p class="card-text">
+                    <strong>Size:</strong> ${drive.size}<br>
+                    <strong>Model:</strong> ${drive.model || 'Unknown'}<br>
+                    ${drive.serial ? `<strong>Serial:</strong> ${drive.serial}<br>` : ''}
+                    ${drive.mount_point ? `<strong>Mounted at:</strong> ${drive.mount_point}<br>` : ''}
+                </p>
+                <div>
+                    ${drive.mounted
+                        ? '<span class="badge bg-secondary">Mounted - Unavailable</span>'
+                        : '<span class="badge bg-success">Available for Benchmark</span>'
+                    }
+                </div>
+            </div>
+        `;
+
+        col.appendChild(card);
+        container.appendChild(col);
+    });
+}
+
+// Render drive selector for benchmark tab (available drives only)
+function renderDriveSelector(data) {
+    const container = document.getElementById('drive-cards');
+    if (!container) return;
+    
+    container.innerHTML = '';
+
+    if (!data.drives || data.drives.length === 0) {
+        container.innerHTML = '<div class="col-12"><p class="text-muted">No drives found.</p></div>';
+        return;
+    }
+
+    // Filter to show only available drives
+    const availableDrives = data.drives.filter(drive => !drive.mounted);
+
+    if (availableDrives.length === 0) {
+        container.innerHTML = '<div class="col-12"><div class="alert alert-warning">No available drives. All drives are mounted.</div></div>';
+        return;
+    }
+
+    availableDrives.forEach(drive => {
+        const col = document.createElement('div');
+        col.className = 'col-md-4 mb-3';
+
+        const cardWrapper = document.createElement('div');
+        cardWrapper.className = 'drive-selector-card';
+        cardWrapper.dataset.drivePath = drive.path;
+
+        // Radio input (hidden)
+        const radio = document.createElement('input');
+        radio.type = 'radio';
+        radio.name = 'selected_drive';
+        radio.value = drive.path;
+        radio.id = `drive-${drive.name}`;
+        radio.className = 'btn-check';
+        radio.setAttribute('autocomplete', 'off');
+
+        // Label as card
+        const label = document.createElement('label');
+        label.htmlFor = `drive-${drive.name}`;
+        label.className = 'btn btn-outline-primary w-100 text-start';
+        label.innerHTML = `
+            <div class="d-flex justify-content-between align-items-start">
+                <div>
+                    <h6 class="mb-1">${drive.name}</h6>
+                    <small class="text-muted">${drive.size} ${drive.model || ''}</small>
+                </div>
+                <div class="text-end">
+                    <small class="text-success">Available</small>
+                </div>
+            </div>
+            ${drive.serial ? `<small class="text-muted d-block mt-1">SN: ${drive.serial}</small>` : ''}
+        `;
+
+        cardWrapper.appendChild(radio);
+        cardWrapper.appendChild(label);
+        col.appendChild(cardWrapper);
+        container.appendChild(col);
+
+        // Add click handler to show selected drive info
+        radio.addEventListener('change', function() {
+            if (this.checked) {
+                selectDrive(drive);
+            }
+        });
+    });
+}
+
+// Handle drive selection
+function selectDrive(drive) {
+    selectedDrive = drive;
+    console.log('Selected drive:', drive);
+    
+    // Update UI to show selection
+    const infoDiv = document.getElementById('selected-drive-info');
+    if (infoDiv) {
+        infoDiv.innerHTML = `
+            <div class="alert alert-success">
+                <strong>Selected:</strong> ${drive.name} (${drive.path})
+                <br><small>${drive.size} - ${drive.model || 'Unknown model'}</small>
+            </div>
+        `;
+    }
+    
+    // Enable benchmark configuration section
+    const configDiv = document.getElementById('benchmark-config');
+    if (configDiv) {
+        configDiv.classList.remove('opacity-50');
+        configDiv.querySelector('.card-body').innerHTML = `
+            <p>Drive <strong>${drive.name}</strong> selected. Configure benchmark parameters below.</p>
+            <!-- Benchmark options will go here -->
+        `;
+    }
+}
+
+// Listen for HTMX events
+document.addEventListener('htmx:afterRequest', function(evt) {
+    // Render drives in home page
+    if (evt.detail.target.id === 'drives-content') {
+        renderDrives(JSON.parse(evt.detail.xhr.response));
+    }
+    
+    // Render drive selector in benchmark page
+    if (evt.detail.target.id === 'drive-cards') {
+        renderDriveSelector(JSON.parse(evt.detail.xhr.response));
+    }
+});
+
+// Listen for HTMX load event as fallback
+document.addEventListener('htmx:load', function(evt) {
+    if (evt.target.id === 'drive-cards') {
+        // HTMX will load the content via hx-get
+        // The afterRequest event will handle rendering
+    }
+});
\ No newline at end of file
diff --git a/templates/base.html b/templates/base.html
new file mode 100644
index 0000000..79b79e5
--- /dev/null
+++ b/templates/base.html
@@ -0,0 +1,53 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Disk Checker - {% block title %}Home{% endblock %}</title>
+    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet">
+    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.10.0/font/bootstrap-icons.css">
+    <script src="https://unpkg.com/htmx.org@1.9.10"></script>
+    <link rel="stylesheet" href="/static/css/style.css">
+    {% block extra_css %}{% endblock %}
+</head>
+<body>
+    <!-- Navigation Bar -->
+    <nav class="navbar navbar-expand-lg navbar-dark bg-dark">
+        <div class="container">
+            <!-- Logo / Brand -->
+            <a class="navbar-brand" href="/">
+                <i class="bi bi-hdd-stack"></i>
+                Disk Checker
+            </a>
+            
+            <!-- Mobile toggle -->
+            <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav">
+                <span class="navbar-toggler-icon"></span>
+            </button>
+            
+            <!-- Navigation Tabs -->
+            <div class="collapse navbar-collapse" id="navbarNav">
+                <ul class="navbar-nav">
+                    {% for nav_item in navigation %}
+                    <li class="nav-item">
+                        <a class="nav-link {% if active_tab == nav_item.name %}active{% endif %}" 
+                           href="{{ nav_item.url }}">
+                            <i class="bi {{ nav_item.icon }}"></i>
+                            {{ nav_item.label }}
+                        </a>
+                    </li>
+                    {% endfor %}
+                </ul>
+            </div>
+        </div>
+    </nav>
+   
+    <!-- Page Content -->
+    <div class="container mt-4">
+        {% block content %}{% endblock %}
+    </div>
+    
+    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/js/bootstrap.bundle.min.js"></script>
+    {% block extra_js %}{% endblock %}
+</body>
+</html>
\ No newline at end of file
diff --git a/templates/benchmark.html b/templates/benchmark.html
new file mode 100644
index 0000000..2f6d600
--- /dev/null
+++ b/templates/benchmark.html
@@ -0,0 +1,50 @@
+{% extends "base.html" %}
+
+{% block title %}Benchmark{% endblock %}
+
+{% block content %}
+<div class="row">
+    <div class="col-12">
+        <h2>Benchmark</h2>
+        <p class="text-muted">Configure and run disk benchmarks.</p>
+        
+        <!-- Drive Selection Section -->
+        <div class="card mb-4">
+            <div class="card-header">
+                <h5 class="mb-0">Select Drive to Benchmark</h5>
+            </div>
+            <div class="card-body">
+                <p class="text-muted">Choose an available drive from the list below.</p>
+                
+                <!-- Drive selector container -->
+                <div id="drive-selector" 
+                     hx-get="/api/v1/drives" 
+                     hx-trigger="load"
+                     hx-target="#drive-cards"
+                     hx-swap="innerHTML">
+                </div>
+                
+                <!-- Drive cards will be rendered here -->
+                <div id="drive-cards" class="row g-3"></div>
+                
+                <!-- Selected drive display -->
+                <div id="selected-drive-info" class="mt-3"></div>
+            </div>
+        </div>
+        
+        <!-- Benchmark Configuration (placeholder for next feature) -->
+        <div class="card" id="benchmark-config">
+            <div class="card-header">
+                <h5 class="mb-0">Benchmark Configuration</h5>
+            </div>
+            <div class="card-body">
+                <p class="text-muted">Select a drive above to configure benchmark parameters.</p>
+            </div>
+        </div>
+    </div>
+</div>
+{% endblock %}
+
+{% block extra_js %}
+<script src="/static/js/main.js"></script>
+{% endblock %}
\ No newline at end of file
diff --git a/templates/index.html b/templates/index.html
new file mode 100644
index 0000000..74845cd
--- /dev/null
+++ b/templates/index.html
@@ -0,0 +1,53 @@
+{% extends "base.html" %}
+
+{% block title %}Home{% endblock %}
+
+{% block content %}
+<div class="row">
+    <div class="col-12">
+        <!--Available tools section-->
+        <h2>Available Benchmarking Tools</h2>
+
+        <!-- Server-side rendered tools -->
+        {% if tools %}
+        <div class="row">
+            {% for tool_name, tool in tools.items() %}
+            <div class="col-md-4 mb-3">
+                <div class="card {% if tool.available %}border-success{% else %}border-secondary{% endif %}">
+                    <div class="card-body">
+                        <h5 class="card-title">{{ tool.name }}</h5>
+                        <p class="card-text">
+                            {% if tool.available %}
+                            <span class="badge bg-success">Available</span>
+                            {% if tool.version %}
+                            <small class="text-muted">{{ tool.version }}</small>
+                            {% endif %}
+                            {% else %}
+                            <span class="badge bg-secondary">Not Installed</span>
+                            {% endif %}
+                        </p>
+                    </div>
+                </div>
+            </div>
+            {% endfor %}
+        </div>
+        {% endif %}
+
+        <!--Available drives section-->
+        <h2 class="mt-5">Available Drives</h2>
+        <p class="text-muted">
+            <i class="bi bi-info-circle"></i>
+            Mounted drives are grayed out and cannot be benchmarked.
+        </p>
+        <div id="drives-list" 
+             hx-get="/api/v1/drives" 
+             hx-trigger="load"
+             hx-target="#drives-content"></div>
+        <div id="drives-content" class="row"></div>
+    </div>
+</div>
+{% endblock %}
+
+{% block extra_js %}
+<script src="/static/js/main.js"></script>
+{% endblock %}
\ No newline at end of file
diff --git a/templates/jobs.html b/templates/jobs.html
new file mode 100644
index 0000000..ced952d
--- /dev/null
+++ b/templates/jobs.html
@@ -0,0 +1,54 @@
+{% extends "base.html" %}
+
+{% block title %}Job Queue{% endblock %}
+
+{% block content %}
+<div class="row">
+    <div class="col-12">
+        <h2>Job Queue</h2>
+        <p class="text-muted">Monitor and manage benchmark jobs.</p>
+        
+        <!-- Jobs list -->
+        <div id="jobs-list" 
+             hx-get="/api/v1/jobs" 
+             hx-trigger="load"
+             hx-target="#jobs-content">
+            <p>Loading jobs...</p>
+        </div>
+        <div id="jobs-content"></div>
+    </div>
+</div>
+{% endblock %}
+
+{% block extra_js %}
+<script>
+    // Load jobs when page loads
+    document.addEventListener('htmx:afterRequest', function(evt) {
+        if (evt.detail.target.id === 'jobs-content') {
+            renderJobs(JSON.parse(evt.detail.xhr.response));
+        }
+    });
+    
+    function renderJobs(jobIds) {
+        const container = document.getElementById('jobs-content');
+        container.innerHTML = '';
+        
+        if (!jobIds || jobIds.length === 0) {
+            container.innerHTML = '<div class="alert alert-info">No jobs in queue.</div>';
+            return;
+        }
+        
+        jobIds.forEach(jobId => {
+            const div = document.createElement('div');
+            div.className = 'card mb-2';
+            div.innerHTML = `
+                <div class="card-body">
+                    <h5 class="card-title">${jobId}</h5>
+                    <p class="card-text text-muted">Job details will appear here...</p>
+                </div>
+            `;
+            container.appendChild(div);
+        });
+    }
+</script>
+{% endblock %}
\ No newline at end of file
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..ca3d1c4
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for disk-checker."""
\ No newline at end of file
diff --git a/tests/test_converter.py b/tests/test_converter.py
new file mode 100644
index 0000000..f9ac54f
--- /dev/null
+++ b/tests/test_converter.py
@@ -0,0 +1,68 @@
+"""Tests for the unit conversion module."""
+
+import numpy as np
+import pytest
+
+from disk_checker.core.converter import to_unit, UNIT_FACTORS, UNIT_LABELS
+
+
+class TestToUnit:
+    """Tests for to_unit function."""
+
+    def test_nanoseconds_to_microseconds(self):
+        """Test conversion from ns to us."""
+        values = np.array([1000, 2000, 3000])
+        result = to_unit(values, "us")
+        expected = np.array([1.0, 2.0, 3.0])
+        np.testing.assert_array_equal(result, expected)
+
+    def test_nanoseconds_to_milliseconds(self):
+        """Test conversion from ns to ms."""
+        values = np.array([1000000, 2000000])
+        result = to_unit(values, "ms")
+        expected = np.array([1.0, 2.0])
+        np.testing.assert_array_equal(result, expected)
+
+    def test_nanoseconds_to_seconds(self):
+        """Test conversion from ns to s."""
+        values = np.array([1000000000, 2000000000])
+        result = to_unit(values, "s")
+        expected = np.array([1.0, 2.0])
+        np.testing.assert_array_equal(result, expected)
+
+    def test_same_unit_returns_same(self):
+        """Test conversion to same unit."""
+        values = np.array([100, 200, 300])
+        result = to_unit(values, "ns")
+        np.testing.assert_array_equal(result, values)
+
+    def test_empty_array(self):
+        """Test conversion with empty array."""
+        values = np.array([])
+        result = to_unit(values, "us")
+        assert len(result) == 0
+
+    def test_single_value(self):
+        """Test conversion with single value."""
+        result = to_unit(1000, "us")
+        assert result == 1.0
+
+
+class TestConstants:
+    """Tests for module constants."""
+
+    def test_unit_factors(self):
+        """Test UNIT_FACTORS contains all expected units."""
+        assert set(UNIT_FACTORS.keys()) == {"ns", "us", "ms", "s"}
+        assert UNIT_FACTORS["ns"] == 1.0
+        assert UNIT_FACTORS["us"] == 1e3
+        assert UNIT_FACTORS["ms"] == 1e6
+        assert UNIT_FACTORS["s"] == 1e9
+
+    def test_unit_labels(self):
+        """Test UNIT_LABELS contains all expected units."""
+        assert set(UNIT_LABELS.keys()) == {"ns", "us", "ms", "s"}
+        assert UNIT_LABELS["ns"] == "ns"
+        assert UNIT_LABELS["us"] == "µs"
+        assert UNIT_LABELS["ms"] == "ms"
+        assert UNIT_LABELS["s"] == "s"
\ No newline at end of file
diff --git a/tests/test_extractor.py b/tests/test_extractor.py
new file mode 100644
index 0000000..d63155e
--- /dev/null
+++ b/tests/test_extractor.py
@@ -0,0 +1,72 @@
+"""Tests for the data extraction module."""
+
+import pytest
+import pandas as pd
+from pathlib import Path
+
+from disk_checker.core.extractor import load_latency_csv
+
+
+class TestLoadLatencyCsv:
+    """Tests for load_latency_csv function."""
+
+    def test_load_valid_csv(self, sample_csv_path):
+        """Test loading a valid fio CSV file."""
+        df = load_latency_csv(str(sample_csv_path))
+        assert not df.empty
+        assert "metric" in df.columns
+        assert "latency_ns" in df.columns
+        assert "count" in df.columns
+
+    def test_returns_long_format(self, sample_csv_path):
+        """Test that output is in long format with metric column."""
+        df = load_latency_csv(str(sample_csv_path))
+        metrics = df["metric"].unique()
+        assert "read_clat" in metrics
+
+    def test_empty_csv_raises(self, empty_csv_path):
+        """Test that empty CSV raises ValueError."""
+        with pytest.raises(ValueError):
+            load_latency_csv(str(empty_csv_path))
+
+    def test_invalid_format_raises(self, invalid_csv_path):
+        """Test that invalid CSV format raises ValueError."""
+        with pytest.raises(ValueError):
+            load_latency_csv(str(invalid_csv_path))
+
+    def test_missing_nsec_column_raises(self, tmp_path):
+        """Test that missing nsec column raises ValueError."""
+        csv_content = "col1,col2\n1,2\n"
+        path = tmp_path / "invalid.csv"
+        path.write_text(csv_content)
+        with pytest.raises(ValueError, match="expected first column to be 'nsec'"):
+            load_latency_csv(str(path))
+
+
+@pytest.fixture
+def sample_csv_path(tmp_path):
+    """Create a sample CSV file for testing."""
+    csv_content = """nsec,read_clat_ns_count,read_clat_ns_cumulative,read_clat_ns_percentile
+19791872,1,1,0.00016775708773695687
+22413312,4,5,0.0008387854386847844
+22675456,9,14,0.0023485992283173965
+"""
+    path = tmp_path / "test.csv"
+    path.write_text(csv_content)
+    return path
+
+
+@pytest.fixture
+def empty_csv_path(tmp_path):
+    """Create an empty CSV file for testing."""
+    path = tmp_path / "empty.csv"
+    path.write_text("nsec\n")
+    return path
+
+
+@pytest.fixture
+def invalid_csv_path(tmp_path):
+    """Create an invalid CSV file for testing."""
+    path = tmp_path / "invalid.csv"
+    path.write_text("col1,col2\n1,2\n")
+    return path
\ No newline at end of file
diff --git a/tests/test_helpers.py b/tests/test_helpers.py
new file mode 100644
index 0000000..52806e3
--- /dev/null
+++ b/tests/test_helpers.py
@@ -0,0 +1,77 @@
+"""Tests for helper functions."""
+
+import pandas as pd
+import pytest
+
+from disk_checker.core.helpers import human_count, percentile_table
+
+
+class TestHumanCount:
+    """Tests for human_count function."""
+
+    def test_small_number(self):
+        """Test formatting of small numbers."""
+        assert human_count(100) == "100"
+        assert human_count(50) == "50"
+
+    def test_thousands(self):
+        """Test formatting of thousands."""
+        assert human_count(1500) == "2k"
+        assert human_count(2500) == "2k"
+        assert human_count(1000) == "1k"
+        assert human_count(999) == "999"
+
+    def test_millions(self):
+        """Test formatting of millions."""
+        assert human_count(1500000) == "1.5M"
+        assert human_count(2750000) == "2.8M"
+
+    def test_billions(self):
+        """Test formatting of billions."""
+        assert human_count(1500000000) == "1.5G"
+        assert human_count(2750000000) == "2.8G"
+
+    def test_zero(self):
+        """Test formatting of zero."""
+        assert human_count(0) == "0"
+
+    def test_position_argument_ignored(self):
+        """Test that _pos argument is ignored."""
+        assert human_count(1000, 0) == "1k"
+
+
+class TestPercentileTable:
+    """Tests for percentile_table function."""
+
+    def test_basic_percentiles(self):
+        """Test basic percentile table generation."""
+        df = pd.DataFrame({
+            "metric": ["read_clat"] * 3,
+            "latency_ns": [1000, 2000, 3000],
+            "count": [1, 2, 1],
+        })
+        result = percentile_table(df, "read_clat", "us", [50, 90])
+        assert "Metric: read_clat" in result
+        assert "total I/Os: 4" in result
+        assert "percentile" in result
+        assert "latency" in result
+
+    def test_missing_metric(self):
+        """Test percentile table with missing metric."""
+        df = pd.DataFrame({
+            "metric": ["read_clat"],
+            "latency_ns": [1000],
+            "count": [1],
+        })
+        result = percentile_table(df, "write_clat", "us", [50])
+        assert "(no data for metric write_clat)" in result
+
+    def test_unit_display(self):
+        """Test that correct unit is displayed."""
+        df = pd.DataFrame({
+            "metric": ["read_clat"],
+            "latency_ns": [1000000],  # 1ms in ns
+            "count": [1],
+        })
+        result = percentile_table(df, "read_clat", "ms", [50])
+        assert "ms" in result
\ No newline at end of file
diff --git a/tests/test_orchestrator.py b/tests/test_orchestrator.py
new file mode 100644
index 0000000..08f8756
--- /dev/null
+++ b/tests/test_orchestrator.py
@@ -0,0 +1,57 @@
+"""Tests for the orchestrator module."""
+
+import asyncio
+import pytest
+from pathlib import Path
+from unittest.mock import AsyncMock, patch
+
+from disk_checker.core.orchestrator import Orchestrator, ToolStatus, JobResult
+
+
+class TestOrchestrator:
+    """Tests for Orchestrator class."""
+
+    @pytest.fixture
+    def orchestrator(self, tmp_path):
+        """Create an orchestrator instance."""
+        return Orchestrator(work_dir=tmp_path)
+
+    def test_initial_state(self, orchestrator):
+        """Test initial orchestrator state."""
+        assert orchestrator.list_jobs() == {}
+
+    def test_run_fio_creates_job(self, orchestrator, tmp_path):
+        """Test that run_fio creates a job entry."""
+        with patch("asyncio.create_subprocess_exec") as mock_exec:
+            mock_exec.return_value = AsyncMock()
+            result = asyncio.get_event_loop().run_until_complete(
+                orchestrator.run_fio("/dev/sda")
+            )
+
+        jobs = orchestrator.list_jobs()
+        assert len(jobs) == 1
+        job = list(jobs.values())[0]
+        assert job.status == ToolStatus.COMPLETED
+        # Note: output_path may not exist in test environment without actual fio
+
+    def test_get_job_status(self, orchestrator, tmp_path):
+        """Test retrieving job status."""
+        with patch("asyncio.create_subprocess_exec") as mock_exec:
+            mock_exec.return_value = AsyncMock()
+            result = asyncio.get_event_loop().run_until_complete(
+                orchestrator.run_fio("/dev/sda")
+            )
+            # result is the output path, job_id is derived from it
+            job_id = f"fio_{result.stem.split('_')[-1]}"
+            # Get the actual job_id from the jobs dict
+            jobs = orchestrator.list_jobs()
+            job_id = list(jobs.keys())[0]
+
+        job = orchestrator.get_job_status(job_id)
+        assert job is not None
+        assert job.status == ToolStatus.COMPLETED
+
+    def test_get_nonexistent_job(self, orchestrator):
+        """Test getting status of non-existent job."""
+        job = orchestrator.get_job_status("nonexistent")
+        assert job is None
\ No newline at end of file
diff --git a/tests/test_plots.py b/tests/test_plots.py
new file mode 100644
index 0000000..3aaa6d7
--- /dev/null
+++ b/tests/test_plots.py
@@ -0,0 +1,134 @@
+"""Tests for the plotting module."""
+
+import pytest
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+import matplotlib
+matplotlib.use("Agg")
+import matplotlib.pyplot as plt
+
+from disk_checker.plotting.plots import draw_histogram, draw_cdf, generate_plot
+import pandas as pd
+
+
+class TestDrawHistogram:
+    """Tests for draw_histogram function."""
+
+    @pytest.fixture
+    def sample_df(self):
+        """Create a sample DataFrame for testing."""
+        return pd.DataFrame({
+            "metric": ["read_clat", "read_clat", "write_clat"],
+            "latency_ns": [1000, 2000, 1500],
+            "count": [1, 2, 1],
+        })
+
+    def test_draws_histogram(self, sample_df, tmp_path):
+        """Test that histogram is drawn without errors."""
+        fig, ax = plt.subplots()
+        draw_histogram(ax, sample_df, ["read_clat"])
+        assert ax.get_title() == "Completion latency distribution"
+        plt.close(fig)
+
+    def test_multiple_metrics(self, sample_df, tmp_path):
+        """Test drawing multiple metrics."""
+        fig, ax = plt.subplots()
+        draw_histogram(ax, sample_df, ["read_clat", "write_clat"])
+        assert len(ax.collections) > 0
+        plt.close(fig)
+
+    def test_log_scale(self, sample_df, tmp_path):
+        """Test logarithmic scale."""
+        fig, ax = plt.subplots()
+        draw_histogram(ax, sample_df, ["read_clat"], log_x=True, log_y=True)
+        assert ax.get_xscale() == "log"
+        assert ax.get_yscale() == "log"
+        plt.close(fig)
+
+
+class TestDrawCdf:
+    """Tests for draw_cdf function."""
+
+    @pytest.fixture
+    def sample_df(self):
+        """Create a sample DataFrame for testing."""
+        return pd.DataFrame({
+            "metric": ["read_clat", "read_clat"],
+            "latency_ns": [1000, 2000],
+            "count": [1, 3],
+        })
+
+    def test_draws_cdf(self, sample_df, tmp_path):
+        """Test that CDF is drawn without errors."""
+        fig, ax = plt.subplots()
+        draw_cdf(ax, sample_df, ["read_clat"])
+        assert ax.get_title() == "Cumulative latency distribution"
+        assert ax.get_ylim() == (0, 100)
+        plt.close(fig)
+
+    def test_log_scale(self, sample_df, tmp_path):
+        """Test logarithmic X scale."""
+        fig, ax = plt.subplots()
+        draw_cdf(ax, sample_df, ["read_clat"], log_x=True)
+        assert ax.get_xscale() == "log"
+        plt.close(fig)
+
+
+class TestGeneratePlot:
+    """Tests for generate_plot function."""
+
+    @pytest.fixture
+    def sample_df(self):
+        """Create a sample DataFrame for testing."""
+        return pd.DataFrame({
+            "metric": ["read_clat", "read_clat"],
+            "latency_ns": [1000, 2000],
+            "count": [1, 3],
+        })
+
+    def test_generates_histogram(self, sample_df, tmp_path):
+        """Test generating histogram plot."""
+        output = tmp_path / "test.png"
+        result = generate_plot(
+            df=sample_df,
+            metrics=["read_clat"],
+            output_path=output,
+        )
+        assert result == output
+        assert output.exists()
+
+    def test_generates_cdf_only(self, sample_df, tmp_path):
+        """Test generating CDF-only plot."""
+        output = tmp_path / "test_cdf.png"
+        result = generate_plot(
+            df=sample_df,
+            metrics=["read_clat"],
+            output_path=output,
+            cdf_only=True,
+        )
+        assert result == output
+        assert output.exists()
+
+    def test_generates_histogram_with_cdf(self, sample_df, tmp_path):
+        """Test generating histogram with CDF below."""
+        output = tmp_path / "test_both.png"
+        result = generate_plot(
+            df=sample_df,
+            metrics=["read_clat"],
+            output_path=output,
+            show_cdf=True,
+        )
+        assert result == output
+        assert output.exists()
+
+    def test_custom_dpi(self, sample_df, tmp_path):
+        """Test custom DPI setting."""
+        output = tmp_path / "test_dpi.png"
+        result = generate_plot(
+            df=sample_df,
+            metrics=["read_clat"],
+            output_path=output,
+            dpi=300,
+        )
+        assert result == output
+        assert output.exists()
\ No newline at end of file
diff --git a/tests/test_web.py b/tests/test_web.py
new file mode 100644
index 0000000..e023ebd
--- /dev/null
+++ b/tests/test_web.py
@@ -0,0 +1,89 @@
+"""Tests for the web backend."""
+
+import pytest
+from fastapi.testclient import TestClient
+from pathlib import Path
+from unittest.mock import AsyncMock, patch
+
+from disk_checker.web.server import app
+
+
+@pytest.fixture
+def client():
+    """Create test client."""
+    return TestClient(app)
+
+
+@pytest.fixture
+def sample_csv_content():
+    """Sample CSV content for testing."""
+    return """nsec,read_clat_ns_count,read_clat_ns_cumulative,read_clat_ns_percentile
+19791872,1,1,0.00016775708773695687
+22413312,4,5,0.0008387854386847844
+22675456,9,14,0.0023485992283173965
+"""
+
+
+@pytest.fixture
+def sample_csv_path(tmp_path, sample_csv_content):
+    """Create sample CSV file."""
+    path = tmp_path / "test.csv"
+    path.write_text(sample_csv_content)
+    return path
+
+
+def test_health_check(client):
+    """Test health check endpoint."""
+    response = client.get("/health")
+    assert response.status_code == 200
+    assert response.json()["status"] == "ok"
+
+
+def test_scan_csv(client, sample_csv_path):
+    """Test CSV scan endpoint."""
+    with open(sample_csv_path, "rb") as f:
+        response = client.post("/api/v1/scan", files={"file": f})
+    assert response.status_code == 200
+    data = response.json()
+    assert "metrics" in data
+    assert len(data["metrics"]) > 0
+
+
+def test_plot_endpoint(client, sample_csv_path):
+    """Test plot generation endpoint."""
+    with open(sample_csv_path, "rb") as f:
+        response = client.post(
+            "/api/v1/plot",
+            files={"file": (sample_csv_path.name, f, "text/csv")},
+            data={"unit": "us"},
+        )
+    assert response.status_code == 200
+    assert response.headers["content-type"] == "image/png"
+
+
+def test_plot_with_options(client, sample_csv_path):
+    """Test plot generation with options."""
+    with open(sample_csv_path, "rb") as f:
+        response = client.post(
+            "/api/v1/plot",
+            files={"file": (sample_csv_path.name, f, "text/csv")},
+            data={
+                "metric": "read_clat",
+                "unit": "ms",
+                "log_x": "true",
+                "cdf": "true",
+            },
+        )
+    assert response.status_code == 200
+
+
+def test_invalid_metric(client, sample_csv_path):
+    """Test invalid metric returns error."""
+    with open(sample_csv_path, "rb") as f:
+        response = client.post(
+            "/api/v1/plot",
+            files={"file": (sample_csv_path.name, f, "text/csv")},
+            data={"metric": "invalid_metric", "unit": "us"},
+        )
+    # Note: endpoint returns 200 and auto-selects best metric when invalid
+    assert response.status_code == 200
\ No newline at end of file