hello_test: create an assert function

hello_test.go

@@ -6,16 +6,19 @@ func TestHello(t *testing.T) {
 	t.Run("Hello someone", func(t *testing.T) {
 		got := Hello("Jason")
 		exp := "Hello Jason"
-		if got != exp {
-			t.Errorf("got %q expected %q", got, exp)
-		}
+		assertCorrectMsg(t, got, exp)
 	})
 
 	t.Run("Hello default", func(t *testing.T) {
 		got := Hello("")
 		exp := "Hello world"
+		assertCorrectMsg(t, got, exp)
+	})
+}
+
+func assertCorrectMsg(t testing.TB, got, exp string) {
+	t.Helper()
 	if got != exp {
 		t.Errorf("got %q expected %q", got, exp)
 	}
-	})
 }