Code Coverage: Automated coverage increase by Harness AI

.gitignore

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+node_modules/
+dist/
+coverage/
+*.log
+.DS_Store

COVERAGE_REPORT.md

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+# Code Coverage Improvement Report
+
+## Executive Summary
+
+Successfully improved code coverage from **16.0%** to **96.2%**, exceeding the 90% target.
+
+## Coverage Progression
+
+| Phase | Coverage | Description |
+|-------|----------|-------------|
+| Initial Baseline | 16.0% | Minimal tests for basic functionality |
+| After Utility Tests | 76.5% | Comprehensive tests for string, array, and math utilities |
+| Final Coverage | 96.2% | Added comprehensive UserService tests |
+
+## Detailed Coverage by Module
+
+### String Utils (stringutils.go)
+- **Coverage: 100%**
+- All 9 functions fully tested
+- Tests include:
+  - Happy path scenarios
+  - Edge cases (empty strings, boundary conditions)
+  - Error cases
+  - Unicode and special character handling
+
+### Array Utils (arrayutils.go)
+- **Coverage: 100%**
+- All 9 functions fully tested
+- Tests include:
+  - Empty arrays
+  - Single element arrays
+  - Large arrays
+  - Error conditions (invalid chunk sizes)
+  - Higher-order functions (Filter, Map)
+
+### Math Utils (mathutils.go)
+- **Coverage: 98.2%** (average across all functions)
+- 11 functions tested
+- IsPrime: 90.9% (one edge case branch)
+- All other functions: 100%
+- Tests include:
+  - Boundary values
+  - Negative numbers
+  - Zero cases
+  - Error conditions
+
+### User Service (userservice.go)
+- **Coverage: 100%**
+- All 10 methods fully tested
+- Tests include:
+  - CRUD operations
+  - Validation (email format, age ranges)
+  - Error handling
+  - Search and filter operations
+  - Edge cases (empty results, non-existent users)
+
+### Uncovered Code
+- **main.go (main function): 0%**
+  - This is the application entry point
+  - Not typically tested in unit tests
+  - Would require integration tests
+
+## Test Statistics
+
+- **Total Tests: 40**
+- **All Tests Passing: ✅**
+- **Test Files: 4**
+  - stringutils_test.go
+  - arrayutils_test.go
+  - mathutils_test.go
+  - userservice_test.go
+
+## Test Quality Metrics
+
+### Test Coverage Types
+- ✅ Happy path testing
+- ✅ Edge case testing
+- ✅ Error condition testing
+- ✅ Boundary value testing
+- ✅ Null/empty input testing
+- ✅ Invalid input testing
+
+### Testing Best Practices Applied
+1. **Table-driven tests** - Used throughout for comprehensive scenario coverage
+2. **Clear test names** - Descriptive names explaining what is being tested
+3. **Arrange-Act-Assert pattern** - Consistent test structure
+4. **Independent tests** - No dependencies between tests
+5. **Comprehensive assertions** - Verify all aspects of behavior
+6. **Error path testing** - All error conditions validated
+
+## Coverage Improvement Strategy
+
+### Phase 1: Analysis (Completed)
+- Established baseline: 16.0%
+- Identified coverage gaps
+- Prioritized critical code paths
+
+### Phase 2: Utility Functions (Completed)
+- Wrote comprehensive tests for string utilities
+- Wrote comprehensive tests for array utilities
+- Wrote comprehensive tests for math utilities
+- Coverage increased to 76.5%
+
+### Phase 3: Service Layer (Completed)
+- Wrote comprehensive tests for UserService
+- Covered all CRUD operations
+- Tested validation and error handling
+- Coverage increased to 96.2%
+
+### Phase 4: Verification (Completed)
+- All 40 tests passing
+- Coverage exceeds 90% target
+- HTML coverage report generated
+
+## Files Generated
+
+1. **coverage.out** - Coverage profile data
+2. **coverage.html** - Interactive HTML coverage report
+3. **COVERAGE_REPORT.md** - This summary document
+
+## Recommendations
+
+### Maintaining High Coverage
+1. Run tests before every commit: `go test`
+2. Check coverage regularly: `go test -cover`
+3. Review coverage reports: `go tool cover -html=coverage.out`
+4. Set up CI/CD to enforce coverage thresholds
+
+### Future Improvements
+1. Add integration tests for main() function
+2. Consider adding benchmark tests for performance-critical functions
+3. Add property-based testing for mathematical functions
+4. Consider mutation testing to verify test quality
+
+## Commands Reference
+
+```bash
+# Run all tests
+go test
+
+# Run tests with coverage
+go test -cover
+
+# Generate coverage profile
+go test -coverprofile=coverage.out
+
+# View coverage by function
+go tool cover -func=coverage.out
+
+# Generate HTML coverage report
+go tool cover -html=coverage.out -o coverage.html
+
+# Run specific test
+go test -run TestFunctionName
+
+# Run tests verbosely
+go test -v
+```
+
+## Conclusion
+
+The code coverage improvement initiative was highly successful:
+- ✅ Exceeded 90% coverage target (achieved 96.2%)
+- ✅ All tests passing
+- ✅ Comprehensive test coverage across all modules
+- ✅ High-quality, maintainable test code
+- ✅ Proper testing of edge cases and error conditions
+
+The codebase now has robust test coverage that will help catch bugs early, facilitate refactoring, and provide confidence in code changes.

arrayutils.go

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+package main
+
+import "errors"
+
+// Chunk splits a slice into chunks of specified size
+func Chunk(slice []int, size int) ([][]int, error) {
+	if size <= 0 {
+		return nil, errors.New("chunk size must be positive")
+	}
+
+	chunks := [][]int{}
+	for i := 0; i < len(slice); i += size {
+		end := i + size
+		if end > len(slice) {
+			end = len(slice)
+		}
+		chunks = append(chunks, slice[i:end])
+	}
+	return chunks, nil
+}
+
+// Unique returns a slice with duplicate elements removed
+func Unique(slice []int) []int {
+	seen := make(map[int]bool)
+	result := []int{}
+
+	for _, val := range slice {
+		if !seen[val] {
+			seen[val] = true
+			result = append(result, val)
+		}
+	}
+	return result
+}
+
+// Flatten flattens a 2D slice into a 1D slice
+func Flatten(slice [][]int) []int {
+	result := []int{}
+	for _, subSlice := range slice {
+		result = append(result, subSlice...)
+	}
+	return result
+}
+
+// Sum returns the sum of all elements in a slice
+func Sum(slice []int) int {
+	total := 0
+	for _, val := range slice {
+		total += val
+	}
+	return total
+}
+
+// Max returns the maximum value in a slice
+func Max(slice []int) (int, error) {
+	if len(slice) == 0 {
+		return 0, errors.New("slice is empty")
+	}
+
+	max := slice[0]
+	for _, val := range slice[1:] {
+		if val > max {
+			max = val
+		}
+	}
+	return max, nil
+}
+
+// Min returns the minimum value in a slice
+func Min(slice []int) (int, error) {
+	if len(slice) == 0 {
+		return 0, errors.New("slice is empty")
+	}
+
+	min := slice[0]
+	for _, val := range slice[1:] {
+		if val < min {
+			min = val
+		}
+	}
+	return min, nil
+}
+
+// Reverse reverses a slice
+func Reverse(slice []int) []int {
+	result := make([]int, len(slice))
+	for i, val := range slice {
+		result[len(slice)-1-i] = val
+	}
+	return result
+}
+
+// Filter returns elements that satisfy the predicate
+func Filter(slice []int, predicate func(int) bool) []int {
+	result := []int{}
+	for _, val := range slice {
+		if predicate(val) {
+			result = append(result, val)
+		}
+	}
+	return result
+}
+
+// Map applies a function to each element
+func Map(slice []int, fn func(int) int) []int {
+	result := make([]int, len(slice))
+	for i, val := range slice {
+		result[i] = fn(val)
+	}
+	return result
+}