golang-testing

Define a slice of anonymous structs with name, inputs, and expected outputs, then loop over cases calling t.Run for each subtest. This pattern covers many scenarios with minimal code and is the standard Go testing idiom.

Write a function starting with Fuzz that accepts *testing.F, add seed corpus entries with f.Add, then define the fuzz function with f.Fuzz. Run it with go test -fuzz=FuzzName -fuzztime=30s; fuzzing requires Go 1.18 or later.

Run go test -coverprofile=coverage.out ./... to generate a coverage profile, then use go tool cover -html=coverage.out for a browser view or -func for per-function percentages. Add -race to combine coverage with race detection.

Define an interface for the dependency, then create a mock struct with function fields matching each method. Inject the mock into the code under test and set the function fields per test case to control behavior and simulate errors.

Testing private functions couples tests to implementation details, making refactors break tests unnecessarily. Test through the public API instead, which verifies actual behavior and keeps tests stable during internal changes.

Use httptest.NewRequest to build a request and httptest.NewRecorder to capture the response, then call the handler directly. Assert on the recorder's status code and body, optionally using table-driven tests for multiple endpoints.