quarto-preview-test

Testing & Quality

Use when testing preview functionality, verifying live reload, or validating preview fixes. Covers starting preview with port/logging, browser verification via /agent-browser, and checking logs/filesystem for artifacts.

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Quarto Preview Test

Interactive testing of quarto preview with automated browser verification.

Tools

Tool	When to use
`/agent-browser`	Preferred. Token-efficient browser automation. Navigate, verify content, screenshot.
Chrome DevTools MCP	Deep debugging: console messages, network requests, DOM inspection.
`jq` / `grep`	Parse debug log output.

Prerequisites

Quarto dev version built (./configure.sh or ./configure.cmd)
Test environment configured (tests/configure-test-env.sh or tests/configure-test-env.ps1)
/agent-browser CLI installed (preferred), OR Chrome + Chrome DevTools MCP connected

Starting Preview

Preview needs the test venv for Jupyter tests. Activate it first (tests/.venv), matching how run-tests.sh / run-tests.ps1 do it.

# Linux/macOS
source tests/.venv/bin/activate
./package/dist/bin/quarto preview <file-or-dir> --no-browser --port 4444

# Windows (Git Bash)
source tests/.venv/Scripts/activate
./package/dist/bin/quarto.cmd preview <file-or-dir> --no-browser --port 4444

Use --no-browser to control browser connection. Use --port for a predictable URL.

With debug logging

./package/dist/bin/quarto preview <file> --no-browser --port 4444 --log-level debug 2>&1 | tee preview.log

In background

# Linux/macOS (after venv activation)
./package/dist/bin/quarto preview <file> --no-browser --port 4444 &
PREVIEW_PID=$!
# ... run verification ...
kill $PREVIEW_PID

# Windows (Git Bash, after venv activation)
./package/dist/bin/quarto.cmd preview <file> --no-browser --port 4444 &
PREVIEW_PID=$!
# ... run verification ...
kill $PREVIEW_PID

Edit-Verify Cycle

The core test pattern:

Start preview with --no-browser --port 4444
Use /agent-browser to navigate to http://localhost:4444/ and verify content
Edit source file, wait 3-5 seconds for re-render
Verify content updated in browser
Check filesystem for unexpected artifacts
Stop preview, verify cleanup

What to Verify

In browser (via /agent-browser): Page loads, content matches source, updates reflect edits.

In terminal/logs: No BadResource errors, no crashes, preview stays responsive.

On filesystem: No orphaned temp files, cleanup happens on exit.

Windows Limitations

On Windows, kill from Git Bash does not trigger Quarto's onCleanup handler (SIGINT doesn't propagate to Windows processes the same way). Cleanup-on-exit verification requires an interactive terminal with Ctrl+C. For automated testing, verify artifacts during preview instead.

Context Types

Preview behaves differently depending on input:

Input	Code path
Single file (no project)	`preview()` -> `renderForPreview()`
File within a project	May redirect to project preview via `serveProject()`
Project directory	`serveProject()` -> `watchProject()`

See llm-docs/preview-architecture.md for the full architecture.

When NOT to Use

Automated smoke tests — use tests/smoke/ instead
Testing render output only (no live preview needed) — use quarto render
CI environments without browser access

Test Matrix

The full test matrix lives in tests/docs/manual/preview/README.md. Test fixtures live alongside it in tests/docs/manual/preview/.

Running specific tests by ID

When invoked with test IDs (e.g., /quarto-preview-test T17 T18):

Read tests/docs/manual/preview/README.md
Find each requested test by its ID (e.g., #### T17:)
Parse the Setup, Steps, and Expected fields
Execute each test following the steps, using the fixtures in tests/docs/manual/preview/
Report PASS/FAIL for each test with the actual vs expected result

Running tests by topic

When invoked with a topic description instead of IDs (e.g., /quarto-preview-test root URL or "run preview tests for single-file"):

Read tests/docs/manual/preview/README.md
Search test titles and descriptions for matches (keywords, issue numbers, feature area)

Present the matched tests to the user for confirmation before running:

Found these matching tests:
- T17: Single-file preview — root URL accessible (#14298)
- T18: Single-file preview — named output URL also accessible
Run these? [Y/n]

Only execute after user confirms

Running without arguments

When invoked without test IDs or topic (e.g., /quarto-preview-test), use the general Edit-Verify Cycle workflow described above for ad-hoc preview testing. The test matrix is for targeted regression testing.

Baseline Comparison

Compare dev build against installed release to distinguish regressions:

quarto --version                        # installed
./package/dist/bin/quarto --version     # dev

If both show the same issue, it's pre-existing.