hello.go

package hello

import "fmt"

func Hello(user string) string {
	hello := "hello " + user
	fmt.Println(hello)
	return hello
}

hello_test.go

package hello

import "testing"

func TestHello(t *testing.T) {
	const user, expected = "samurai20000", "hello samurai20000"
	result := Hello(user)
	if result != expected {
		t.Errorf("Hello(%v)=%v expected: %v", user, result, expected)
	}
}