How to Write Tests for CLI Applications in Go

Use the testing package to create a test file ending in _test.go and call testing.MainStart or testing.Main to execute your CLI's main function with specific arguments.

package main

import (
	"os"
	"testing"
)

func TestMain(t *testing.T) {
	// Simulate CLI arguments: go run mkzip.go zoneinfo.zip
	os.Args = []string{"mkzip.go", "zoneinfo.zip"}
	main()
}

This approach allows you to test the CLI behavior directly by injecting arguments into os.Args before calling main() within the test function.

To test a command-line tool, you write a special file that runs your program's main code but lets you pretend the user typed specific commands. It's like running a simulation where you control exactly what buttons the user presses to see if the program reacts correctly.