Go TDD Skill

Enforces test-driven development methodology for Go code using idiomatic Go testing patterns.

TDD Cycle

RED     → Write failing table-driven test
GREEN   → Implement minimal code to pass
REFACTOR → Improve code, tests stay green
REPEAT  → Next test case

Workflow

1. Define Types/Interfaces: Scaffold function signatures first
2. Write Table-Driven Tests: Create comprehensive test cases (RED)
3. Run Tests: Verify tests fail for the right reason
4. Implement Code: Write minimal code to pass (GREEN)
5. Refactor: Improve while keeping tests green
6. Check Coverage: Ensure 80%+ coverage

Test Patterns

Table-Driven Tests

tests := []struct {
    name     string
    input    InputType
    want     OutputType
    wantErr  bool
}{
    {"case 1", input1, want1, false},
    {"case 2", input2, want2, true},
}

for _, tt := range tests {
    t.Run(tt.name, func(t *testing.T) {
        got, err := Function(tt.input)
        // assertions
    })
}

Parallel Tests

for _, tt := range tests {
    tt := tt // Capture
    t.Run(tt.name, func(t *testing.T) {
        t.Parallel()
        // test body
    })
}

Test Helpers

func setupTestDB(t *testing.T) *sql.DB {
    t.Helper()
    db := createDB()
    t.Cleanup(func() { db.Close() })
    return db
}

Coverage Commands

go test -cover ./...                    # Basic coverage
go test -coverprofile=coverage.out ./...# Coverage profile
go tool cover -html=coverage.out        # View in browser
go tool cover -func=coverage.out        # Coverage by function
go test -race -cover ./...              # With race detection

Coverage Targets

Code Type	Target
Critical business logic	100%
Public APIs	90%+
General code	80%+
Generated code	Exclude

Best Practices

DO:

• Write test FIRST, before any implementation
• Run tests after each change
• Use table-driven tests for comprehensive coverage
• Test behavior, not implementation details
• Include edge cases (empty, nil, max values)
• Always run with -race flag

DON'T:

• Write implementation before tests
• Skip the RED phase
• Test private functions directly
• Use time.Sleep in tests
• Ignore flaky tests