| name | testing-wallaby |
| description | Debug and fix failing tests using Wallaby.js MCP tools. Use when investigating test failures, debugging test errors, inspecting runtime values, checking code coverage, or updating snapshots. |
Testing with Wallaby
Use Wallaby MCP tools as the primary way to work with tests. Fall back to terminal only if Wallaby is unavailable.
Debug Workflow
1. Identify failures
- Broad:
wallaby_failingTests — all failing tests in the project
- By file:
wallaby_failingTestsForFile — failures related to a specific source or test file
- By line:
wallaby_failingTestsForFileAndLine — failures covering a specific line
Each returns test name, test ID, errors with stack traces, runtime logs, and coverage percentage.
2. Narrow down with coverage
wallaby_coveredLinesForFile — which lines a file has covered, optionally filtered by test IDwallaby_coveredLinesForTest — all files/lines a specific test covers
Use coverage to find the implementation code a failing test actually executes.
3. Inspect runtime values
wallaby_runtimeValues — value of an expression at a file/line across all testswallaby_runtimeValuesByTest — value of an expression at a file/line for a specific test
Required params: file, line (1-based, count blank lines), lineContent, expression. For runtimeValuesByTest, also testId.
4. Fix the code
Apply the fix based on evidence from steps 1-3.
5. Verify the fix
wallaby_testById — re-check a specific test by its IDwallaby_failingTests — confirm no remaining failures
Iterate steps 3-5 until the test passes.
6. Update snapshots (if needed)
wallaby_updateTestSnapshots — update snapshots for one test (by test ID)wallaby_updateFileSnapshots — update all snapshots in/covering a filewallaby_updateProjectSnapshots — update every snapshot in the project
Discovery Tools
Use these when exploring tests, not just debugging failures:
wallaby_allTests — list every test in the projectwallaby_allTestsForFile — tests related to a specific filewallaby_allTestsForFileAndLine — tests covering a specific file and line
Principles
- Always cite runtime values and coverage data to justify conclusions.
- Explain reasoning step by step.
- Keep iterating with updated Wallaby data until the test passes.
