Svelte Test Fix Processor

Troubleshoot and fix failing tests in Svelte and SvelteKit projects by analyzing error messages, identifying failure patterns, and applying targeted fixes.

When to Use This Command

Run this command when...

• Your Svelte component tests are failing and you need systematic diagnosis of the root cause from error messages and stack traces
• You have flaky tests that pass intermittently and need stabilization through proper async handling, cleanup, or mocking
• Your test suite broke after a Svelte, SvelteKit, or testing library version upgrade and needs compatibility fixes

Do NOT use this command when...

• You need to write tests from scratch -- use the test creation command instead
• Your tests are passing but you want to improve coverage or refactor test structure

Quick Start

Copy
# .claude/commands/svelte-test-fix-processor.md
# Fix failing Svelte tests
Fix tests: $ARGUMENTS

Copy
# Run the command
claude "svelte-test-fix-processor fix TypeError: Cannot read properties of undefined in UserProfile.test.ts"

Expected output:
- Error analysis with root cause identification
- Missing mock or setup dependency detection
- Code fix for the failing test
- Regression prevention recommendation
- Verification command to confirm the fix

Core Concepts

Concept	Description
Error Classification	Categorizing failures as setup, rendering, async, mock, or assertion errors
Flaky Test Detection	Identifying tests that fail intermittently due to timing or state leaks
Mock Diagnosis	Detecting missing or incorrectly configured mocks for SvelteKit modules
Cleanup Verification	Ensuring component cleanup runs between tests to prevent state leaks
Version Compatibility	Checking testing library API changes across version upgrades

Test Fix Pipeline:

  Failing Test + Error Message
       |
  [Classify Error Type]
       |
  +----+----+----+----+
  |    |    |    |    |
 Setup Render Async Mock Assert
  |    |    |    |    |
  [Identify Root Cause]
       |
  [Generate Fix]
       |
  [Verify Fix Passes]
       |
  Stable Test

Configuration

Parameter	Default	Description
Test Runner	Auto-detect	Vitest, Jest, or Playwright based on project config
Error Source	Test output	Error message, file path, or test name to diagnose
Fix Scope	Single test	Whether to fix one test or scan for similar failures
Verification	Run after fix	Whether to execute the test after applying the fix
Regression Check	Suggest guard	Whether to recommend preventing similar future failures

Best Practices

1. Include the full error message -- copy the complete error output including stack trace in your arguments for accurate root cause analysis
2. Mention recent changes -- if tests broke after an upgrade or refactor, state what changed so the fixer can correlate the failure with the change
3. Fix one test at a time -- resolve failures individually to understand each root cause rather than applying broad fixes that may mask underlying issues
4. Check for state leaks -- if multiple tests fail, the first failure may contaminate subsequent tests through leaked state. Fix the first failure first
5. Update test utilities -- after fixing, check if your test helper functions need the same fix applied to prevent similar failures in future tests

Common Issues

1. Cannot find module errors -- SvelteKit alias imports ($lib/, $app/) need mock configuration in vitest.config.ts. Add the resolve.alias section matching your svelte.config.js
2. Component renders but events do not fire -- use await fireEvent and await tick() to ensure Svelte reactive updates complete before asserting on event effects
3. Tests pass individually but fail together -- state from one test leaks into the next. Add cleanup() calls in afterEach and verify mocks are reset between tests