Testing in Go

go/go.mod

@@ -0,0 +1,3 @@
+module hello
+
+go 1.17

go/hello.go

@@ -2,6 +2,28 @@ package main
 
 import "fmt"
 
-func main() {
+const englishHelloPrefix = "Hello, "
-	fmt.Println("Hello, World")
+const welsh = "Welsh"
+const welshHelloPrefix = "Helo, "
+
+func Hello(name string, language string) string {
+	if name == "" {
+		name = "World"
+	}
+
+	return greetingPrefix(language) + name
+}
+
+func greetingPrefix(language string) (prefix string) {
+	prefix = englishHelloPrefix
+
+	if language == welsh {
+		prefix = welshHelloPrefix
+	}
+
+	return
+}
+
+func main() {
+	fmt.Println(Hello("Oliver", ""))
 }

go/hello_test.go

@@ -0,0 +1,34 @@
+package main
+
+import "testing"
+
+func TestHello(t *testing.T) {
+	assertCorrectMessage := func(t testing.TB, got string, want string) {
+		t.Helper()
+
+		if got != want {
+			t.Errorf("got %q want %q", got, want)
+		}
+	}
+
+	t.Run("saying hello to people", func (t *testing.T) {
+		got := Hello("Oliver", "")
+		want := "Hello, Oliver"
+
+		assertCorrectMessage(t, got, want)
+	})
+
+	t.Run("say 'Hello, World' when an empty string is supplied", func (t *testing.T) {
+		got := Hello("", "")
+		want := "Hello, World"
+
+		assertCorrectMessage(t, got, want)
+	})
+
+	t.Run("in Welsh", func (t *testing.T) {
+		got := Hello("Oliver", "Welsh")
+		want := "Helo, Oliver"
+
+		assertCorrectMessage(t, got, want)
+	})
+}