Merge pull request #20 from samuelematias/lesson20

Lesson 20: Stubbing asynchronous methods using mockito

README.md

@@ -42,6 +42,8 @@ Calculator - [Caster.IO](https://caster.io) project to showcase testing techniqu
 
 [Lesson 19: Stubbing synchronous methods with mock](https://caster.io/lessons/lesson-19-stubbing-synchronous-methods-with-mockito) 👉🏾 [Branch](https://github.com/samuelematias/calculator_app/tree/lesson19)
 
+[Lesson 20: Stubbing asynchronous methods using mockito](https://caster.io/lessons/lesson-20-stubbing-asynchronous-methods-using-mockito) 👉🏾 [Branch](https://github.com/samuelematias/calculator_app/tree/lesson20)
+
 ## License
 
 ```

lib/main.dart

@@ -1,4 +1,6 @@
 import 'package:calculator_app/models/models.dart';
+import 'package:calculator_app/pi.dart';
+import 'package:calculator_app/power_of_two.dart';
 import 'package:calculator_app/two_digit_operation.dart';
 import 'package:flutter/material.dart';
 import 'package:calculator/calculator.dart';
@@ -17,28 +19,34 @@ class CalculatorApp extends StatelessWidget {
         body: SingleChildScrollView(
           child: Padding(
             padding: EdgeInsets.all(12),
-            child: Column(
-              children: [
-                TwoDigitOperation(
-                  calculator: calculator,
-                  operation: Operations.add,
-                ),
-                Divider(),
-                TwoDigitOperation(
-                  calculator: calculator,
-                  operation: Operations.substract,
-                ),
-                Divider(),
-                TwoDigitOperation(
-                  calculator: calculator,
-                  operation: Operations.multiply,
-                ),
-                Divider(),
-                TwoDigitOperation(
-                  calculator: calculator,
-                  operation: Operations.divide,
-                ),
-              ],
+            child: SafeArea(
+              child: Column(
+                children: [
+                  PowerOfTwo(calculator: calculator),
+                  Divider(),
+                  Pi(calculator: calculator),
+                  Divider(),
+                  TwoDigitOperation(
+                    calculator: calculator,
+                    operation: Operations.add,
+                  ),
+                  Divider(),
+                  TwoDigitOperation(
+                    calculator: calculator,
+                    operation: Operations.substract,
+                  ),
+                  Divider(),
+                  TwoDigitOperation(
+                    calculator: calculator,
+                    operation: Operations.multiply,
+                  ),
+                  Divider(),
+                  TwoDigitOperation(
+                    calculator: calculator,
+                    operation: Operations.divide,
+                  ),
+                ],
+              ),
             ),
           ),
         ),

lib/pi.dart

@@ -0,0 +1,37 @@
+import 'package:calculator/calculator.dart';
+import 'package:flutter/material.dart';
+
+class Pi extends StatelessWidget {
+  Pi({Key key, @required Calculator calculator})
+      : assert(calculator != null),
+        _calculator = calculator,
+        super(key: key);
+
+  final Calculator _calculator;
+
+  @override
+  Widget build(BuildContext context) {
+    String _result;
+
+    return StreamBuilder<double>(
+      stream: _calculator.pi(),
+      initialData: null,
+      builder: (context, snapshot) {
+        if (snapshot.data != null) {
+          _result = snapshot.data.toString();
+        }
+        return Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Text(
+              _result != null
+                  ? 'The latest known value of pi is $_result'
+                  : 'Calculating pi...',
+              style: Theme.of(context).textTheme.headline5,
+            ),
+          ],
+        );
+      },
+    );
+  }
+}

lib/power_of_two.dart

@@ -0,0 +1,70 @@
+import 'package:calculator/calculator.dart';
+import 'package:flutter/material.dart';
+
+class PowerOfTwo extends StatefulWidget {
+  const PowerOfTwo({
+    Key key,
+    @required Calculator calculator,
+  })  : assert(calculator != null),
+        _calculator = calculator,
+        super(key: key);
+
+  final Calculator _calculator;
+
+  @override
+  State<StatefulWidget> createState() => _PowerOfTwoState();
+}
+
+class _PowerOfTwoState extends State<PowerOfTwo> {
+  final _controller = TextEditingController();
+
+  String _result;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller.addListener(_getResult);
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        TextFormField(
+          key: const Key('textField_powerOfTwo'),
+          controller: _controller,
+          keyboardType: TextInputType.number,
+        ),
+        Text(
+          'to the power of two',
+          style: Theme.of(context).textTheme.headline5,
+        ),
+        Text(
+          'is ${_result ?? '???'}',
+          style: Theme.of(context).textTheme.headline5,
+        ),
+      ],
+    );
+  }
+
+  void _getResult() async {
+    try {
+      final input = double.tryParse(_controller.text);
+      final powerOfTwoResult = await widget._calculator.powerOfTwo(input);
+      setState(() {
+        _result = powerOfTwoResult.toString();
+      });
+    } catch (_) {
+      setState(() {
+        _result = null;
+      });
+    }
+  }
+}

packages/calculator/lib/src/calculator.dart

@@ -14,5 +14,10 @@ class Calculator {
   Future<double> powerOfTwo(double a) =>
       Future.delayed(const Duration(seconds: 1), () => a * a);
 
-  Stream<double> pi() => Stream.fromIterable([3, 3.1, 3.14, 3.141, 3.1415]);
+  Stream<double> pi() => Stream.periodic(
+        const Duration(seconds: 1),
+        (count) => _piValues[count],
+      );
+
+  List<double> _piValues = [3, 3.1, 3.14, 3.141, 3.1415];
 }

test/pi_test.dart

@@ -0,0 +1,49 @@
+import 'package:calculator/calculator.dart';
+import 'package:calculator_app/pi.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/mockito.dart';
+
+class MockCalculator extends Mock implements Calculator {}
+
+void main() {
+  Calculator calculator;
+
+  setUp(() {
+    calculator = MockCalculator();
+  });
+
+  group('Pi', () {
+    testWidgets('renders the result provided by the calculator',
+        (tester) async {
+      when(calculator.pi()).thenAnswer((realInvocation) => Stream.periodic(
+            Duration(milliseconds: 400),
+            (eventIndex) {
+              if (eventIndex == 0) return 3.1;
+              if (eventIndex == 1) return 3.14;
+              return null;
+            },
+          ));
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: Pi(
+              calculator: calculator,
+            ),
+          ),
+        ),
+      );
+      expect(find.text('Calculating pi...'), findsOneWidget);
+      await tester.pumpAndSettle(Duration(milliseconds: 400));
+      expect(
+        find.text('The latest known value of pi is 3.1'),
+        findsOneWidget,
+      );
+      await tester.pumpAndSettle(Duration(milliseconds: 400));
+      expect(
+        find.text('The latest known value of pi is 3.14'),
+        findsOneWidget,
+      );
+    });
+  });
+}

test/power_of_two_test.dart

@@ -0,0 +1,35 @@
+import 'package:calculator/calculator.dart';
+import 'package:calculator_app/power_of_two.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/mockito.dart';
+
+class MockCalculator extends Mock implements Calculator {}
+
+void main() {
+  Calculator calculator;
+
+  setUp(() {
+    calculator = MockCalculator();
+  });
+
+  group('PowerOfTwo', () {
+    testWidgets('renders the result provided by the calculator',
+        (tester) async {
+      when(calculator.powerOfTwo(5))
+          .thenAnswer((realInvocation) => Future.value(100));
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: PowerOfTwo(
+              calculator: calculator,
+            ),
+          ),
+        ),
+      );
+      await tester.enterText(find.byKey(Key('textField_powerOfTwo')), '5');
+      await tester.pumpAndSettle();
+      expect(find.text('is 100.0'), findsOneWidget);
+    });
+  });
+}