captjay98/testing-patterns

Testing Patterns

You are a QA specialist for LivestockAI, expert in Vitest, fast-check, and integration testing.

Test Commands

# IMPORTANT: Use "bun run test" not "bun test"
bun run test              # Unit tests (vitest)
bun run test:integration  # Integration tests (requires DATABASE_URL_TEST)
bun run test:all          # All tests
bun run test:coverage     # Coverage report

Property-Based Tests (fast-check)

Use for mathematical invariants and business logic:

import { describe, it, expect } from 'vitest'
import * as fc from 'fast-check'

describe('calculateFCR', () => {
  it('should always be positive when inputs are positive', () => {
    fc.assert(
      fc.property(
        fc.double({ min: 0.01, max: 10000, noNaN: true }),
        fc.double({ min: 0.01, max: 10000, noNaN: true }),
        (feed, gain) => {
          const fcr = calculateFCR(feed, gain)
          expect(fcr).toBeGreaterThan(0)
        },
      ),
    )
  })

  it('should return 0 when weight gain is 0 or negative', () => {
    fc.assert(
      fc.property(
        fc.double({ min: 0.01, max: 10000, noNaN: true }),
        fc.double({ max: 0, noNaN: true }),
        (feed, gain) => {
          expect(calculateFCR(feed, gain)).toBe(0)
        },
      ),
    )
  })
})

fast-check Best Practices

// Always use noNaN: true for doubles
fc.double({ min: 0, max: 1000, noNaN: true })

// Always use noInvalidDate: true for dates
fc.date({
  min: new Date('2020-01-01'),
  max: new Date('2030-01-01'),
  noInvalidDate: true,
})

// Constrain longitude to avoid date line issues
fc.double({ min: -170, max: 170, noNaN: true })

Integration Tests

Setup Pattern

import { afterAll, afterEach, beforeEach, describe, expect, it } from 'vitest'
import {
  closeTestDb,
  getTestDb,
  resetTestDb,
  seedTestUser,
  seedTestFarm,
  truncateAllTables,
} from '../../helpers/db-integration'

describe('Batch Integration Tests', () => {
  beforeEach(async () => {
    await truncateAllTables() // Clean slate
  })

  afterEach(() => {
    resetTestDb() // Clear transaction state (NOT closeTestDb!)
  })

  afterAll(async () => {
    await closeTestDb() // Only here!
  })

  it('should create batch', async () => {
    // Use unique identifiers
    const { userId } = await seedTestUser({
      email: `test-${Date.now()}@example.com`,
    })
    const { farmId } = await seedTestFarm(userId)

    const db = getTestDb()
    // ... test code
  })
})

Critical Rules

1. Use truncateAllTables() in beforeEach() - Reset database state
2. Use resetTestDb() in afterEach() - Clear transaction state
3. Use closeTestDb() in afterAll() ONLY - Don't destroy connection early
4. Use unique identifiers - Prevent duplicate key errors

Unit Tests

import { describe, it, expect } from 'vitest'

describe('validateBatchData', () => {
  it('should return null for valid data', () => {
    const result = validateBatchData({
      batchName: 'Test Batch',
      initialQuantity: 100,
      costPerUnit: 50,
    })
    expect(result).toBeNull()
  })

  it('should return error for negative quantity', () => {
    const result = validateBatchData({
      batchName: 'Test',
      initialQuantity: -1,
      costPerUnit: 50,
    })
    expect(result).toBe('Quantity must be positive')
  })
})

Test File Organization

tests/
├── features/
│   ├── batches/
│   │   ├── batches.test.ts           # Unit tests
│   │   └── batches.property.test.ts  # Property tests
│   └── ...
├── integration/
│   ├── batches.integration.test.ts   # DB tests
│   └── ...
└── helpers/
    ├── db-integration.ts             # Test DB helpers
    └── db-mock.ts                    # Mock helpers

Mocking Patterns

import { vi } from 'vitest'

// Mock server function
vi.mock('~/features/batches/server', () => ({
  getBatchesFn: vi.fn().mockResolvedValue([]),
}))

// Mock database
vi.mock('~/lib/db', () => ({
  getDb: vi.fn().mockResolvedValue(mockDb),
}))