Add special case for empty string

hello/hello.go

@@ -5,6 +5,10 @@ import "fmt"
 const englishHelloPrefix = "Hello, "
 
 func Hello(name string) string {
+	if name == "" {
+		name = "World"
+	}
+
 	return englishHelloPrefix + name
 }
 

hello/hello_test.go

@@ -3,9 +3,20 @@ package main
 import "testing"
 
 func TestHello(t *testing.T) {
+	t.Run("saying hello to people", func(t *testing.T) {
 		got := Hello("Chris")
 		want := "Hello, Chris"
+		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)
+	})
+}
 
+func assertCorrectMessage(t testing.TB, got, want string) {
+	t.Helper()
 	if got != want {
 		t.Errorf("got %q want %q", got, want)
 	}