golang-testing-patterns

Go Testing Patterns

Modern testing patterns for Go following 2025-2026 best practices.

Table-Driven Tests

The idiomatic Go approach for comprehensive testing.

Basic structure:

func TestFeature(t *testing.T) {
	tests := []struct {
		name     string
		input    string
		expected int
		wantErr  bool
	}{
		{
			name:     "valid input",
			input:    "hello",
			expected: 5,
			wantErr:  false,
		},
		{
			name:     "empty input",
			input:    "",
			expected: 0,
			wantErr:  true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := ProcessString(tt.input)
			
			if tt.wantErr {
				if err == nil {
					t.Errorf("expected error, got nil")
				}
				return
			}
			
			if err != nil {
				t.Fatalf("unexpected error: %v", err)
			}
			
			if got != tt.expected {
				t.Errorf("got %d, want %d", got, tt.expected)
			}
		})
	}
}

Using Subtests with t.Run()

Benefits:

• Clear failure messages showing which case failed
• Can run specific tests: go test -run TestFeature/valid_input
• Parallel execution support

Pattern:

for _, tt := range tests {
	t.Run(tt.name, func(t *testing.T) {
		t.Parallel() // Run subtests in parallel
		// ... test logic
	})
}

Test Organization

File structure:

• Tests live alongside code: service.go → service_test.go
• Integration tests in separate package: service_integration_test.go
• Shared test utilities: test/util/ or testutil/

Test function naming:

// Unit tests
func TestSessionService_CreateSession(t *testing.T) {}
func TestSessionService_CreateSession_ValidationError(t *testing.T) {}

// Integration tests
func TestSessionService_Integration(t *testing.T) {}

Setup and Teardown

Using t.Cleanup():

func TestWithCleanup(t *testing.T) {
	// Setup
	db := setupTestDB(t)
	t.Cleanup(func() {
		db.Close() // Always runs, even if test fails
	})
	
	// Test logic
	// ...
}

Setup once for all subtests:

func TestSuite(t *testing.T) {
	// Shared setup
	db := setupTestDB(t)
	t.Cleanup(func() { db.Close() })
	
	t.Run("test1", func(t *testing.T) {
		// Uses shared db
	})
	
	t.Run("test2", func(t *testing.T) {
		// Uses shared db
	})
}