gen_expects 0.1.0

Code generator for testing expect statements.

gen_expects

gen_expects is a code generator for expect statements found in Flutter widgets tests.

Rather than generating a .dart test file, you insert a genExpect call within your widget test:

void main() {
    testWidgets('Confirm all widgets appear', (WidgetTester tester) async {
        await tester.pumpWidget(const MyApp());

        await genExpects(tester);
    });
}

and the genExpects function walks the widget tree and outputs expect statements to the debug console or terminal:

/// Replace your call to generateExpects with the code below.
expect(find.byType(MyHomePage), findsOneWidget);
expect(find.byKey(MainKeys.appBar), findsOneWidget);
expect(find.byType(Fab), findsOneWidget);
expect(find.text('You have pushed the button this many times:'), findsOneWidget);
expect(find.text('0'), findsOneWidget);
expect(find.text('Flutter Demo Home Page'), findsOneWidget);

Following the instructions in the first line of the output that reads /// Replace your call to generateExpects with the code below, you copy the statements and paste them into your test:

void main() {
    testWidgets('Confirm all widgets appear', (WidgetTester tester) async {
        await tester.pumpWidget(const MyApp());

        expect(find.byType(MyHomePage), findsOneWidget);
        expect(find.byKey(MainKeys.appBar), findsOneWidget);
        expect(find.byType(Fab), findsOneWidget);
        expect(find.text('You have pushed the button this many times:'), findsOneWidget);
        expect(find.text('0'), findsOneWidget);
        expect(find.text('Flutter Demo Home Page'), findsOneWidget);
    });
}

And voila! You have written your widget's first test!

The details

The widget tree of your test app can be quite large, so rather than include all widgets and generating dozens or hundreds of expects, genExpects generates expects for:

• Widgets with types passed to the widgetTypes parameter.
• Text widgets.
• Widgets with keys formatted by gen_key.

Expects for widget types

To pass widget types to widgetTypes put them in a Set:

final Set<Type> myWidgetTypes = <Type>{
  Fab,
  MyHomePage,
};

And then pass the Set to genExpects:

 await genExpects(tester, widgetTypes: myWidgetTypes);

genExpects generates an expect statement for every widgetType found:

/// Replace your call to generateExpects with the code below.
expect(find.byType(MyHomePage), findsOneWidget);
expect(find.byType(Fab), findsOneWidget);

Expects for Text widgets

Text widgets always generates expect statements:

/// Replace your call to generateExpects with the code below.
expect(find.text('You have pushed the button this many times:'), findsOneWidget);
expect(find.text('0'), findsOneWidget);
expect(find.text('Flutter Demo Home Page'), findsOneWidget);

Expects for widgets with keys

genExpects also creates expects for widgets with keys formatted by gen_key. Please see the gen_key package for more detail:

/// Replace your call to generateExpects with the code below.
expect(find.byKey(MainKeys.appBar), findsOneWidget);

Use after gestures, too

genExpects generates diff outputs when run in the same widget test. E.g.,

    testWidgets('Confirm all widgets appear', (WidgetTester tester) async {
        await tester.pumpWidget(const MyApp());

        genExpects(tester);              // <- Outputs all found expects
        tester.tap(find.byType(Fab));    // <- Gesture
        genExpects(tester);              // <- Outputs only expects that changed
    });

Because the second call to genExpects only outputs changes, it is handy for writing tests with gestures and for debugging.

That's it!

For questions or anything else gen_expects, feel free to create an issue of contact me.