[Coverage Improvement] Add comprehensive unit tests for BAIStatistic component

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Goal and Rationale

This PR adds comprehensive unit tests for the BAIStatistic component in the backend.ai-ui package, significantly improving test coverage from 0% to 100% (statements).

Why this matters:

• BAIStatistic is a reusable statistics display component used across the application for showing resource usage metrics
• Ensures proper number formatting, infinity handling, and progress bar rendering
• Prevents regressions in critical data display features
• Part of systematic test coverage improvement plan for backend.ai-ui components

Approach

Testing Strategy

• Comprehensive unit testing using Jest and React Testing Library
• 40 test cases covering all component behaviors and edge cases
• Test categories: Basic rendering, number formatting, infinity handling, progress bars, percentage calculation, edge cases, integration tests

Test Implementation Details

Test Categories:

1. Basic Rendering (4 tests) - Title, current value, units, combined display
2. Number Formatting (6 tests) - Decimal precision, trailing zeros, large/small numbers
3. Infinity Handling (4 tests) - Infinity values, custom display strings, negative infinity
4. Progress Bar Rendering (5 tests) - Hidden/normal/ghost modes, undefined total, custom steps
5. Percentage Calculation (8 tests) - 0%, 50%, 100%, edge cases with infinity/zero
6. Edge Cases (7 tests) - Undefined/zero/negative values, precision, styling
7. ReactNode Title Support (2 tests) - JSX elements and complex nodes as titles
8. Integration Tests (3 tests) - Complete component with all props, decimal combinations

Impact Measurement

Coverage Results

Target file: packages/backend.ai-ui/src/components/BAIStatistic.tsx (141 lines)

Metric	Before	After	Improvement
Statements	0%	100%	+100%
Branches	0%	95.83%	+95.83%
Functions	0%	100%	+100%
Lines	0%	100%	+100%

Uncovered lines: 50, 88 (minor conditional branches not affecting core functionality)

Test Suite Results

• ✅ All 40 new tests passing
• ✅ No regressions (102 total tests, up from 62)
• ✅ ESLint and Prettier validation passed
• ✅ Edge cases covered: infinity values, zero division, precision handling

Overall Project Impact

backend.ai-ui Package:

Metric	Before	After	Change
Test files	4	5	+1
Total tests	62	102	+40 tests
Overall coverage	54.78%	58.71%	+3.93%

Trade-offs

Pros

✅ 100% statement coverage - All code paths tested
✅ 95.83% branch coverage - Nearly complete branch coverage
✅ Zero regressions - All existing tests continue to pass
✅ Production-ready - Tests follow best practices and repository patterns
✅ Maintainable - Clear test names and well-organized structure
✅ Comprehensive edge case coverage - Handles infinity, zero division, precision

Cons

⚠️ Test file size - 432 lines for 141-line source (~3:1 ratio)

• Justified by comprehensive coverage of all rendering paths and calculations
  ⚠️ Progress bar testing - Uses presence checks rather than exact percentage values
• Ant Design component internals tested separately; we verify integration
  ⚠️ Two uncovered lines - Lines 50, 88 are minor conditional branches
• Would require complex test setup for minimal additional value

Validation

Testing Approach

All tests use Jest with React Testing Library:

• Component rendering validation using render() and screen queries
• Number formatting validation with various precision levels
• Infinity handling verification with translation mocks
• Progress bar presence and configuration testing
• Edge case validation including zero, negative, and undefined values

Success Criteria Met

✅ All 40 tests pass consistently
✅ 100% statement coverage achieved
✅ 95.83% branch coverage achieved
✅ No lint errors or warnings
✅ No impact on existing tests (62 → 102 tests, all passing)
✅ Pre-commit hooks pass (ESLint + Prettier)

Reproducibility

Setup Commands

# From repository root
cd /home/runner/work/backend.ai-webui/backend.ai-webui

# Install dependencies
pnpm install

# Navigate to backend.ai-ui package
cd packages/backend.ai-ui

Running Tests

# Run tests for this specific file
NODE_OPTIONS='--no-deprecation' npx jest src/components/BAIStatistic.test.tsx

# Run with coverage
NODE_OPTIONS='--no-deprecation' npx jest src/components/BAIStatistic.test.tsx --coverage --collectCoverageFrom='src/components/BAIStatistic.tsx'

# Run all backend.ai-ui tests with coverage
NODE_OPTIONS='--no-deprecation' npx jest --coverage

Expected Results

PASS src/components/BAIStatistic.test.tsx
  BAIStatistic
    Basic Rendering
      ✓ should render title correctly
      ✓ should render current value without total
      ✓ should render unit when provided
      ✓ should render with both current and total values
    Number Formatting
      ✓ should format decimal numbers with default precision (2)
      ✓ should format decimal numbers with custom precision
      ... (34 more tests)

Test Suites: 5 passed, 5 total
Tests:       102 passed, 102 total (40 new)
Snapshots:   3 passed, 3 total
Time:        ~3.6s

Coverage Summary:
File              | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
------------------|---------|----------|---------|---------|-------------------
BAIStatistic.tsx  |     100 |    95.83 |     100 |     100 | 50,88
All files         |   58.71 |    42.16 |   44.73 |   60.70 |

Future Work

Based on the research plan in discussion #4760, the next high-priority areas for test coverage improvement are:

1. Other backend.ai-ui components with 0% coverage:

   • BAIButton.tsx - Button component with async action support
   • BAIBackButton.tsx - Navigation back button component
   • BAIFetchKeyButton.tsx - Fetch key control component
   • BAITag.tsx - Tag display component
   • BAISelect.tsx - Enhanced select component

2. React project helpers in /react/src/helper/:

   • customThemeConfig.ts - Theme loading and configuration logic
   • react-to-webcomponent.tsx - React component wrapper logic
   • bui-language.ts - i18n language mappings (simple constants)

3. React project hooks in /react/src/hooks/:

   • useThemeMode.tsx - Theme management hook
   • useValidateServiceName.tsx - Service name validation logic
   • useValidateSessionName.tsx - Session name validation logic

---

Related Discussion: #4760 (Daily Test Coverage Improver - Research and Plan)
Branch: test/bai-statistic-coverage
Files Changed: 1 file, +432 lines

AI generated by Daily Test Coverage Improver

AI generated by Daily Test Coverage Improver