Useless Test Detector

Detects test files that don't actually test real implementations.

Based on real-world experience cleaning up test suites where tests create mock objects, assert on hardcoded values, or test JavaScript/TypeScript built-ins instead of actual application logic.

Installation

npm install --save-dev @mathonsunday/useless-test-detector

Or run directly with npx:

npx @mathonsunday/useless-test-detector

Usage

CLI

# Scan default directories (src, api)
useless-tests

# Scan custom directories
useless-tests --dirs src,tests,lib

# Only show high confidence results
useless-tests --min-confidence high

# Output as JSON
useless-tests --json > report.json

Programmatic API

import { detectUselessTests } from '@mathonsunday/useless-test-detector';

const results = detectUselessTests({
  directories: ['src', 'api'],
  minConfidence: 'medium',
});

for (const test of results) {
  console.log(test.file, test.confidence, test.reasons);
}

What It Detects

The tool looks for these anti-patterns:

1. Inline implementations: Tests that define their own EventBuffer, Parser, etc. instead of importing the real one
2. Type-only tests: Tests that only verify TypeScript types, not runtime behavior
3. Mock-only tests: Tests that create mock objects and assert on hardcoded values
4. No source imports: Tests that don't import anything from the actual codebase
5. Admission comments: Tests with comments like "In a real test, this would..."
6. Built-in testing: Tests that only verify JavaScript's typeof or other built-ins
7. Fake integration tests: "Integration" tests that never make HTTP requests

Example Output

🔍 Found 3 suspicious test file(s):

🔴 src/__tests__/events.fixed.test.ts
   Confidence: HIGH | Lines: 407
   Reasons:
     - Defines 3 inline implementation(s) instead of importing real ones
     - Creates 12 mock objects and asserts on hardcoded values
     - No imports from actual implementation (only test utilities)

🟡 api/__tests__/types.test.ts
   Confidence: MEDIUM | Lines: 121
   Reasons:
     - Appears to test TypeScript types, not runtime behavior
     - More than 50% of assertions test JavaScript built-ins (typeof, etc)

💡 Recommendation:
   Review these files manually. High confidence files are likely useless.
   Delete files that don't import and test actual implementations.

Philosophy

Not all "bad" tests are useless, but tests that don't exercise real code paths provide zero value and create false confidence.

This tool flags obvious cases where tests:

• Don't import the code they claim to test
• Only test TypeScript's type system (which already runs at compile time)
• Create inline mocks that duplicate production logic

License

MIT