The Go Programming Language

11.1 The go test Tool

The go test subcommand is a test driver for Go packages that are organized according to certain conventions. In a package directory, files whose names end with _test.go are not part of the package ordinarily built by go build but are a part of it when built by go test.

Within *_test.go files, three kinds of functions are treated specially: tests, benchmarks, and examples. A test function, which is a function whose name begins with Test, exercises some program logic for correct behavior; go test calls the test function and reports the result, which is either PASS or FAIL. A benchmark function has a name beginning with Benchmark and measures the performance of some operation; go test reports the mean execution time ...