Know which lines your tests missed — without leaving the editor.
You run pytest. You get 73%. But 27% of what? Finding uncovered lines means opening a browser report, hunting for your file, and mentally mapping line numbers back to your code. Coverage Visualizer cuts all of that — green and red highlights appear inline, right where you write, the moment you run your tests.
Auto-run on test save — write a test, hit save, and pytest runs automatically in the background. No terminal, no command — the extension detects the file change, waits 2 seconds for you to finish typing, then kicks off a full coverage run. The status bar shows a spinner while it runs so you always know something is happening. Turn it off via autoRunOnTestChange if your suite is too slow to run on every save.
Inline highlights — covered lines get a green background, missed lines get red, and overview ruler markers appear along the right edge so you can spot gaps in a file without scrolling a single line. Open any Python file after running coverage and the highlights are already there.
Interactive dashboard — a full coverage report inside VS Code, no browser needed. The ring chart shows your overall percentage at a glance; the file table lists every file sorted by coverage with a progress bar per row. Click any filename and the editor jumps straight to that file.
CodeLens — a coverage percentage appears above every def and class as you work, updated live whenever coverage changes. At a glance you can see which functions are well-tested and which are being ignored, without opening any report.
Sidebar tree view — the Coverage panel in the Explorer sidebar stays open as you work and shows every file with a green check, yellow warning, or red cross depending on your configured thresholds. No need to open the dashboard to know where you stand.
Hover tooltips — hover any highlighted line and a tooltip confirms whether that exact line is covered or not. Useful when you want to verify that a specific branch or edge case was actually exercised by your tests.
Status bar — your overall coverage percentage sits in the bottom status bar at all times. Click it to open the dashboard. When a coverage run is in progress the percentage is replaced with a spinner so you know it's updating.
| Format | How to generate |
|---|---|
coverage.json |
pytest --cov=. --cov-report=json |
coverage.xml |
pytest --cov=. --cov-report=xml |
.coverage |
pytest --cov=. (raw SQLite, no JSON step) |
No Python runtime required — the extension reads all three formats natively.
Search for Python Coverage Visualizer in the Extensions panel (Cmd+Shift+X / Ctrl+Shift+X) and click Install.
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Install pytest-cov in your Python project:
pip install pytest-cov
-
Open the Command Palette (
Cmd+Shift+P/Ctrl+Shift+P) and run Coverage Visualizer: Show Coverage. The extension runs pytest and generates coverage automatically. -
Green and red highlights appear across all open Python files immediately.
From this point, save any test file and coverage updates on its own — no command needed.
| Command | What it does |
|---|---|
Coverage Visualizer: Show Coverage |
Load coverage and apply highlights to open files |
Coverage Visualizer: Show Dashboard |
Open the interactive coverage dashboard |
Coverage Visualizer: Clear Coverage |
Remove all highlights and reset state |
Open Settings (Cmd+,) and search for Coverage Visualizer, or add to settings.json:
| Setting | Default | Description |
|---|---|---|
coverageVisualizer.autoRunOnTestChange |
true |
Re-run pytest automatically when a test file is saved |
coverageVisualizer.autoReloadOnChange |
true |
Auto-reload decorations when coverage files change on disk |
coverageVisualizer.thresholdGood |
80 |
% at or above which a file shows green in the sidebar |
coverageVisualizer.thresholdWarn |
50 |
% at or above which a file shows yellow (below → red) |
coverageVisualizer.excludeTestFiles |
true |
Skip highlights and CodeLens on test files (test_*.py, *_test.py, tests/ dirs) |
coverageVisualizer.enableCodeLens |
true |
Show coverage % above def / class definitions |
coverageVisualizer.enableHoverMessages |
true |
Show covered / not-covered tooltip on hover |
coverageVisualizer.coveredHighlightColor |
rgba(0, 180, 0, 0.10) |
Background color for covered lines |
coverageVisualizer.uncoveredHighlightColor |
rgba(220, 50, 50, 0.10) |
Background color for uncovered lines |