write-test

name	write-test
description	Write a failing test for a reproduced Metabase bug. Invoked from the /repro workflow when status is REPRODUCED. Determines test type (Clojure/Jest/Cypress), finds the right test file, writes a minimal failing test, runs it, and saves a patch.
allowed-tools	Read, Edit, Write, Grep, Glob, mcp__metabase-repro__run_test, mcp__metabase-repro__save_test_patch, mcp__metabase-repro__repl_eval

Write Failing Test

This skill is invoked from the /repro workflow. The issue ID, repro dir, reproduction status, and root cause are in conversation context from prior phases.

Determine Test Type

Bug Type	Test Type	Location
Backend logic, query processor, API	Clojure unit test	test/metabase/...
Frontend UI behavior, rendering	Jest unit/component test	frontend/test/... or co-located *.unit.spec.ts/*.unit.spec.tsx
End-to-end user workflow, UI interaction	Cypress acceptance test	e2e/test/scenarios/...
Mixed (backend + frontend)	Both — Clojure test for data + frontend/e2e test for UI

Find Relevant Test File

Use the root cause to identify source file(s), then locate the corresponding test file:

Backend: src/metabase/foo/bar.clj → test/metabase/foo/bar_test.clj Frontend: frontend/src/metabase/foo/Bar.tsx → frontend/src/metabase/foo/Bar.unit.spec.tsx or frontend/test/metabase/foo/Bar.unit.spec.tsx E2E: UI workflow → e2e/test/scenarios/<category>/foo.cy.spec.ts

Use Grep to search for existing tests related to the buggy function/component. Consult CLAUDE.md in the source worktree for test conventions.

Choose Test Approach

Backend (Clojure):

Root Cause Type	Test Approach
Query processor bug	mt/process-query or qp/process-query
API endpoint bug	mt/user-http-request
Model / data bug	mt/with-temp + t2/select
Pure logic / edge case	Direct function call with specific inputs

Frontend (TypeScript):

Root Cause Type	Test Approach
Component rendering bug	Jest + React Testing Library — render component, assert DOM
User interaction bug	Cypress — visit page, interact, assert visible result
Data display / formatting	Jest unit test on the formatting/transform function
State management bug	Jest — test reducer/action/selector with specific inputs

Look at existing tests in the file for patterns to follow.

Write the Test

Add a new test to the appropriate test file in ./repro/<ISSUE-ID>/source/. The test should:

• Be minimal — only test the specific failing behavior
• Follow existing patterns in the file (imports, fixtures, helpers, assertion style)
• Have a descriptive name referencing the issue: e.g., (deftest issue-12345-test ...), it("should handle X (issue #12345)"), it("should not show X when Y (metabase#12345)")
• Assert the correct/expected behavior — the test should FAIL against the buggy code

Run the Test

mcp__metabase-repro__run_test(repro_dir="repro/<ISSUE-ID>", test_file="test/metabase/foo/bar_test.clj")

• Clojure tests (.clj): Connects to running REPL, adds test/dev paths, requires namespace, runs tests.
• Jest tests (.unit.spec.ts(x)): Runs yarn test-unit in the source worktree.
• Cypress tests (.cy.spec.ts): Runs yarn test-cypress-run with CYPRESS_BASE_URL set.

The tool reports whether the test failed (expected — demonstrates the bug) or passed (unexpected — revisit test logic).

Generate and Save Diff

mcp__metabase-repro__save_test_patch(repro_dir="repro/<ISSUE-ID>")

Saves all changes (including new untracked files) to ./repro/<ISSUE-ID>/test-diff.patch.

Troubleshooting

• Edit tool failures: Re-read the file and retry once. If still failing, use Write tool for the complete file. Do NOT use Bash workarounds (cat >>, cp, python3 -c).
• Bash restrictions in CI: Many Bash commands are blocked. Always use run_test MCP tool — do NOT attempt raw shell commands.
• Can't write a useful test: Note the attempt and reason in the report, move on to Phase 6.
• run_test fails twice: Write an inline REPL snippet instead or skip test execution — the patch is still valuable.
• Large enterprise tests: If run_test times out on a large file in enterprise/backend/test/, write a minimal inline REPL snippet instead.
• Node version errors in CI: Do NOT attempt manual yarn/jest/cypress. Document as "verified by code review, could not execute in CI due to Node version mismatch".
• Jest/Cypress tooling failures: Save the test patch — it's valid evidence even without execution. Note the tooling error in the report.
• run_test returns nil: Ensure setup_worktree was called before start_metabase. If Metabase was started first, restart it to pick up test paths.
• Test namespaces unavailable: Restart Metabase after setup_worktree.
• Dynamic column aliases: For tests involving lib/desired-column-alias, retrieve the alias dynamically from lib/returned-columns rather than hardcoding. Aliases differ by metadata provider.