Code snippets for how to write unit tests in flutter

future_callback_test.dart

  test('testing future callback', () {
    int number = 10;
    Future<int> futureNumber = Future.value(number);
    futureNumber.then((val) {
      expect(val, 10);
    });
  });

future_value_test.dart

  test('testing future values', () async {
    int number = 10;
    Future<int> futureNumber = Future.value(number);
    expect(await futureNumber, 10);
  });

grouping_test.dart

  group('Dart integers', () {
    test('should be summed correctly', () {
      expect(1 + 3, 4);
    });

    test('should be multiplied correctly', () {
      expect(6 * 2, 12);
    });

    test('should work with modulo operator', () {
      expect(11 % 5, 1);
    });
  });

hello_world_test.dart

import 'package:flutter_test/flutter_test.dart';

void main() {
  test('hello world test', () {
    int myNumber = 8;
    expect(myNumber, 8);
  });
}

setup_test_.dart

  group('Dart integers', () {
    int intToTest;
    setUp(() {
      intToTest = 0;
    });

    test('should increment correctly', () {
      expect(++intToTest, 1);
    });

    test('should decrement correctly', () {
      expect(--intToTest, -1);
    });
  });

stream_test.dart

  test('testing streams', () {
    Stream<String> pineappleStream() async* {
      yield "fresh pineapple";
      yield "another fresh pineapple";
    }

    pineappleStream();

    expectLater(pineappleStream(),
        emitsInOrder(["fresh pineapple", "another fresh pineapple"]));
  });

test_iterable_matchers.dart

  test('iterable matchers', () {
    List numbers = [1, 2, 3, 4, 5, 10];
    expect(numbers, anyElement(4));
    expect(numbers, containsAll([2, 1, 3, 10, 5, 4]));
    expect(numbers, containsAllInOrder([1, 2, 3, 4, 5, 10]));
  });

test_string_matchers.dart

  test('string matchers', () {
    expect('the_value', 'the_value');
    expect('the_value', startsWith('the'));
    expect('the_value', endsWith('value'));
    expect(' value  ', equalsIgnoringWhitespace('value'));
    expect('The_Value', equalsIgnoringCase('the_value'));
  });