Unit test coverage above 60%

Having test files is necessary but not sufficient — a test suite that only renders components without crashing and ignores business logic in src/lib/ provides false confidence. ISO 25010:2011 §6.5.5 requires that reliability verification covers the critical paths. A payment calculation function, a permission check, or a data transformation that is never tested will eventually receive a change that breaks it; without a coverage gate, no one learns about it until a user reports a wrong order total or a privilege escalation.

Prioritize business logic over UI rendering — pure functions in src/lib/, src/utils/, and src/services/ are the highest-return coverage targets. Enforce a minimum in your test config:

// vitest.config.ts
import { defineConfig } from 'vitest/config'
export default defineConfig({
  test: {
    coverage: {
      provider: 'v8',
      thresholds: {
        lines: 60,
        functions: 60,
        branches: 50,
      },
      exclude: ['**/*.config.*', 'src/app/**', 'src/components/**'],
    },
  },
})

Run npx vitest run --coverage to see your current baseline before writing new tests.

• ID: code-quality-essentials.testing.unit-coverage

• Severity: medium

• What to look for: Estimate coverage by comparing the number of test files to source files containing business logic. Focus on src/lib/, src/utils/, src/services/, src/hooks/, and similar directories — not UI component files or page files, which are harder to unit test and often better covered by integration tests. Look for coverage configuration in jest.config.* or vitest.config.* — presence of coverageThreshold (Jest) or thresholds (Vitest) means the project enforces minimum coverage. Check CI workflows for a coverage step. A project with many test files but only testing trivial components (renders without crashing) while leaving core data transformation logic untested still fails this check.

• Pass criteria: At least 60% of business logic modules (lib, utils, services, hooks) have corresponding tests with substantive assertions. Coverage tooling is configured or the project clearly covers the majority of critical paths.

• Fail criteria: Few or scattered tests; core business logic files have no corresponding tests; test-to-source ratio below 30% for non-trivial codebases.

• Skip (N/A) when: No test files exist (covered by the previous check).

• Detail on fail: "Estimated coverage below 60%; core logic in src/lib/ appears untested; only UI smoke tests found" (adjust message to what you found)

• Remediation: Prioritize testing business logic over UI rendering. Focus on pure functions first — they're easiest to test and carry the most risk when broken:

  // vitest.config.ts — enforce coverage minimums
  import { defineConfig } from 'vitest/config'
  export default defineConfig({
    test: {
      coverage: {
        provider: 'v8',
        thresholds: {
          lines: 60,
          functions: 60,
          branches: 50,
        },
        exclude: ['**/*.config.*', 'src/app/**', 'src/components/**'],
      },
    },
  })
  

  Run npx vitest run --coverage to see your current baseline before writing tests.