gen_expects

Code generator that walks the widget tree of a test app and generates expect statements for Flutter widgets tests.

How to use GenExpects

Insert a call to genExpects into your widget test:

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

        await genExpects(tester);
    });
}

GenExpects walks the widget tree of your test app and generates expect statements. Rather than generating a .dart test file, GenExpects outputs 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 of type ValueKey(<enum value>)
• Widgets with keys formatted by gen_keys.

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 of type ValueKey(<enum type>)

GenExpects supports ValueKey for enum types. Typically, if you have a class named MyClass, create an enum for storing keys. GenExpects looks for keys in enum format and exports them to expects. (Note that GenExpects generates expect statements only for public keys . Private enums (e.g., _MyClassKeys) are not supported.)

To created enum keys:

class MyClass extends StatelessWidget {
    :
    Container(key: const ValueKey(MyClassKeys.topContainer);
    :
}

enum MyClassKeys {
    topContainer,
}

GenExpects will generate:

/// Replace your call to generateExpects with the code below.
expect(find.byKey(const ValueKey(MyClassKeys.topContainer)), findsOneWidget);

Expects for widgets with keys

GenExpects also creates expects for widgets with keys formatted by gen_keys. Please see the gen_keys 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 GenExpects, feel free to create an issue or contact me.