dict: refacto test for error handling

dictionary/dictionary_test.go

@@ -2,11 +2,19 @@ package dictionary
 
 import "testing"
 
-func assertStrings(t testing.TB, got, want string) {
+func assertStrings(t testing.TB, got, want, given string) {
 	t.Helper()
 
 	if got != want {
-		t.Errorf("got %q want %q given %q", got, want, "test")
+		t.Errorf("got %q want %q given %q", got, want, given)
+	}
+}
+
+func assertError(t testing.TB, got, want error) {
+	t.Helper()
+
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
 	}
 }
 
@@ -17,16 +25,14 @@ func TestSearch(t *testing.T) {
 		got, _ := dictionary.Search("test")
 		want := "this is just a test"
 
-		assertStrings(t, got, want)
+		assertStrings(t, got, want, "test")
 	})
 
 	t.Run("unknown word", func(t *testing.T) {
 		_, err := dictionary.Search("undefined")
-		want := "could not find the word you were looking for"
 		if err == nil {
 			t.Fatal("expected to get an error")
 		}
-
+		assertError(t, err, ErrNotFound)
-		assertStrings(t, err.Error(), want)
 	})
 }