Test files present and organized

A codebase with no test files has no automated verification that the core logic works correctly after a change. Every refactor, dependency upgrade, or new feature becomes a manual regression risk. ISO 25010:2011 §6.5.5 identifies absence of test infrastructure as a reliability defect. For AI-built projects specifically, the lack of tests is a compounding risk: the original author may not remember the edge cases, and future changes can silently break behavior that was never encoded as an assertion.

Set up a test framework appropriate for your stack. For Next.js/React with TypeScript, Vitest + Testing Library is the standard starting point.

npm install -D vitest @testing-library/react @testing-library/user-event jsdom

Add to package.json:

{
  "scripts": {
    "test": "vitest",
    "test:coverage": "vitest run --coverage"
  }
}

Create your first test co-located with the module it covers:

// src/lib/format-price.test.ts
import { describe, it, expect } from 'vitest'
import { formatPrice } from './format-price'

describe('formatPrice', () => {
  it('formats a whole dollar amount', () => {
    expect(formatPrice(1000)).toBe('$10.00')
  })
  it('returns "Free" for zero', () => {
    expect(formatPrice(0)).toBe('Free')
  })
})

• ID: code-quality-essentials.testing.test-files-present

• Severity: medium

• What to look for: Search the project for test files using these patterns: **/*.test.ts, **/*.test.tsx, **/*.spec.ts, **/*.spec.tsx, **/__tests__/**. Estimate the ratio of test files to source files — aim for at least 50% of business logic modules having a corresponding test. Check whether tests are co-located with source files (e.g., utils/parse.ts and utils/parse.test.ts side-by-side) or collected in a __tests__ directory. Examine package.json for a test script — its absence suggests testing is not part of the development workflow. Also check whether a test framework (jest, vitest, mocha) is present in devDependencies.

• Pass criteria: Test files are present covering at least 50% of business logic modules. A test script is defined in package.json. A test framework is in devDependencies.

• Fail criteria: No test files found anywhere in the project, or only placeholder/skeleton test files with no actual assertions.

• Skip (N/A) when: Project is purely a static asset collection with no custom code logic (no JavaScript/TypeScript modules).

• Detail on fail: "No test files (*.test.ts, *.spec.ts, __tests__/) found; testing framework not configured in package.json"

• Remediation: Set up a test framework appropriate for your stack. For Next.js/React with TypeScript, Vitest or Jest with Testing Library is standard:

  npm install -D vitest @testing-library/react @testing-library/user-event jsdom
  

  Add to package.json:

  {
    "scripts": {
      "test": "vitest",
      "test:coverage": "vitest run --coverage"
    }
  }
  

  Create your first test alongside the module it covers:

  // src/lib/format-price.test.ts
  import { describe, it, expect } from 'vitest'
  import { formatPrice } from './format-price'
  
  describe('formatPrice', () => {
    it('formats a whole dollar amount', () => {
      expect(formatPrice(1000)).toBe('$10.00')
    })
    it('returns "Free" for zero', () => {
      expect(formatPrice(0)).toBe('Free')
    })
  })