go test user_test.go user.go

user.go

package user

import "fmt"

func ShowUsers() int {
	return 0
}

func main() {
	fmt.Println("vim-go")
}

user_test.go

package user

import "testing"

func TestHelloWorld(t *testing.T) {
	if ShowUsers() != 0 {
		t.Errorf("something wrong")
	}
}