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Tests that don't actually check anything

TSsenior

Main has `calculateDiscount.ts` with no tests. Leadership wants coverage pushed to 95%. A colleague sent a PR — a new file with 5 tests. All green, coverage jumped. But you know: coverage ≠ quality. Walk the diff and find the tests that don't actually check anything.

PR: lesson.typescript +31 −05 проблем

1-// calculateDiscount.test.ts — new file

1+import { describe, it, expect, vi } from 'vitest'

2+import { calculateDiscount } from './calculateDiscount'

3+import { db } from './db'

5+vi.mock('./db')

7+describe('calculateDiscount', () => {

8+ it('should work', () => {

9+ const result = calculateDiscount(100, 'SILVER')

10+ expect(result).toBeDefined()

11+ })

12+

13+ it('applies discount', () => {

14+ const result = calculateDiscount(100, 'GOLD')

15+ expect(result).not.toBe(100)

16+ })

17+

18+ it('handles edge case', () => {

19+ expect(() => calculateDiscount(0, 'SILVER')).not.toThrow()

20+ })

21+

22+ it('saves to db', async () => {

23+ vi.mocked(db.discounts.save).mockResolvedValue({ id: '1' })

24+ await calculateDiscount(100, 'GOLD')

25+ expect(db.discounts.save).toHaveBeenCalled()

26+ })

27+

28+ it('handles invalid tier', () => {

29+ const result = calculateDiscount(100, 'INVALID')

30+ expect(result).toBe(result)

31+ })

32+})

Шаг 1 из 7

Coverage ≠ Quality

95% coverage doesn't mean "good tests". A test can just call the function and check nothing — coverage goes up, but when a regression happens the test is still green. Bad-test markers: 1. `toBeDefined()`, `toBeTruthy()` on the result — only catches null/undefined. 2. `not.toBe(something)`, `not.toEqual` — pass for almost any value. 3. `not.toThrow()` — only "no exception", not the result. 4. `toHaveBeenCalled()` without arguments — doesn't check the call data. 5. Tautologies like `expect(x).toBe(x)`. 6. `it('should work')`, `it('works')` — no behavior description. Walk the tests and find all these patterns.