golang-testing

Define a slice of anonymous structs holding test case inputs and expected outputs, then loop over them calling t.Run with each case name. This pattern gives comprehensive coverage with minimal code and clear failure messages per case.

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

Define an interface for the dependency, then create a mock struct with function fields matching each interface method. Tests inject the mock and set behavior per case, avoiding external libraries for most scenarios.

Yes, call t.Parallel() inside a test or subtest to run it concurrently with other parallel tests. Capture the range variable with tt := tt before the subtest to avoid sharing loop state across goroutines.

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. Combine with -race to detect data races during the same run.

Flakiness usually comes from time.Sleep calls, shared state, or uncontrolled concurrency. Replace sleeps with channels or conditions, and run go test -count=10 -race ./... to surface intermittent failures and data races.