Go has a lightweight test framework composed of the go test command and the testing package.

You write a test by creating a file with a name ending in _test.go that contains functions named TestXXX with signature func (t *testing.T). The test framework runs each such function; if the function calls a failure function such as t.Error or t.Fail, the test is considered to have failed.

Add a test to the morestrings package by creating the file $HOME/hello/morestrings/reverse_test.go containing the following Go code.

package morestrings

import "testing"

func TestReverseRunes(t *testing.T) {
	cases := []struct {
		in, want string
		{"Hello, world", "dlrow ,olleH"},
		{"Hello, 世界", "界世 ,olleH"},
		{"", ""},
	for _, c := range cases {
		got := ReverseRunes(c.in)
		if got != c.want {
			t.Errorf("ReverseRunes(%q) == %q, want %q", c.in, got, c.want)

Then run the test with go test:

$ go test
ok  	example.com/user/morestrings 0.165s

Run go help test and see the testing package documentation for more detail.

Related Reading

How to Write Go Code