🦾

Gherkin Integration Test

GitHub

https://github.com/codaveto/gherkin_integration_test

Pub.dev

https://pub.dev/packages/gherkin_integration_test

🦾 Gherkin Integration Test

❗

The example project has a test folder where the example project is being fully tested with this framework.

This package is based on the Behaviour Driven Development (BDD) language called Gherkin. This language enables us as developers to design and execute tests in an intuitive and readable way. For people who have a little less experience with development, these tests are also easy to understand because the syntax is very similar to English.

Most tests look something like this:

Feature: This feature shows an example

    Scenario: It shows a good example
      Given we start without an example
      When an example gets created
      Then the example should explode

In this same way we have built our framework, we have the following classes at our disposal:

IntegrationTest
IntegrationFeature
IntegrationScenario
IntegrationExample
IntegrationStep (abstract)

Given
When
Then
And
But

From top to bottom, each class may contain a number of the class below it (one to many). A IntegrationTest may contain multiple IntegrationFeature which in turn may contain multiple IntegrationScenario which in turn may contain multiple IntegrationExample and IntegrationStep.

🛠 Implementation

Start by creating a test class that inherits the IntegrationTest class. Then create a constructor that takes no arguments but does call the superclass with a description and (for now) an empty list of features.

class DummyIntegrationTest extends IntegrationTest {
  DummyIntegrationTest()
      : super(
          description: 'All integration tests regarding dummies',
          features: [],
        );
}

📲 Features

In the features list we can now define our first IntegrationFeature. We give it a name and (for now) an empty list of scenarios.

class DummyIntegrationTest extends IntegrationTest {
  DummyIntegrationTest()
      : super(
          description: 'All integration tests regarding dummies',
          features: [
            IntegrationFeature(
              description: 'Saving of dummies',
              scenarios: [],
            ),
          ],
        );
}

🤝 Scenarios

Now it's time to think about what kind of scenarios might occur in your test. For this example we will use ’a successful save’ and ‘an unsuccessful save’ as possible scenarios.

We use the IntegrationScenario class to create both scenarios and place them in the empty list. We also pass in a description and this time an empty list of steps.

class DummyIntegrationTest extends IntegrationTest {
  DummyIntegrationTest()
      : super(
          description: 'All integration tests regarding dummies',
          features: [
            IntegrationFeature(
              description: 'Saving of dummies',
              scenarios: [
                IntegrationScenario(
                  description: 'Saving a good dummy should succeed',
                  steps: [],
                ),
                IntegrationScenario(
                  description: 'Saving a bad dummy should fail',
                  steps: [],
                ),
              ],
            ),
          ],
        );
}

🐾 Steps

Now comes the good part. For each scenario, we may define steps. We have access to Given, When, Then, And and But. All of these steps do basically the same thing in the background, but by using them correctly, you learn to plan, work out and execute your tests in an intuitive and proper BDD way.

Each step requires a description and a callback. The callback for the IntegrationTests looks as follows and grants access to the following parameters:

/// Callback used to provide the necessary tools to execute an [IntegrationStep].
typedef IntegrationStepCallback<Example extends IntegrationExample?> = FutureOr<void> Function(
  WidgetTester tester,
  IntegrationLog log,
  IntegrationBox box,
  IntegrationMocks mocks, [
  Example? example,
  IntegrationTestWidgetsFlutterBinding? binding,
]);

WidgetTester tester

Class that programmatically interacts with widgets and the test environment (directly from Flutter’s integration_test package).

Log log

Class that allows for subtle logging of steps information in your tests.

IntegrationBox box

This box is basically a map that may be used to write and read values that need to persist throughout a series of steps inside a IntegrationScenario. Any value that you box.write(key, value) will be retrievable in all IntegrationStep's after that or until removed or until all steps have been executed. Reading a value with box.read(key) will automatically cast it to the Type that you specify. So reading an int like this → final int value = box.read(myIntValue) would automatically cast it to an int (🆒).

Using the box may look like this:

[
  Given(
    'This is an example for the IntegrationBox',
    (tester, log, box, mocks, [example, binding]) {
      box.write('isExample', true);
    },
  ),
  When(
    'we write some values',
    (tester, log, box, mocks, [example, binding]) {
      box.write('exampleValue', 1);
      box.write('mood', 'happy');
    },
  ),
  Then(
    'all the values should be accessible up until the last step.',
    (tester, log, box, mocks, [example, binding]) {
      final bool isExample = box.read('isExample');
      final int exampleValue = box.read('exampleValue');
      final bool mood = box.read('mood');
      expect(isExample, true);
      expect(exampleValue, 1);
      expect(mood, 'happy');
    },
  ),
]

IntegrationMocks mocks

A box that exists and persists throughout your entire IntegrationTest, IntegrationFeature and/or IntegrationScenario. You may have optionally use this box to store mocks that you need so you may later retrieve them to stub methods to your liking. You may set up your mocks from any method but it’s recommended to use the setUpMocks method because that runs before any other method inside any of the test classes and will allow you to keep a good overview.

IntegrationExample? example

Optional ‘Scenario Outline’ examples that may have been specified inside a IntegrationScenario like this:

IntegrationScenario(
  description: 'Saving a good dummy should succeed',
  examples: [
    const IntegrationExample(values: [1]),
    const IntegrationExample(values: [5]),
    const IntegrationExample(values: [10]),
  ],
)

This IntegrationScenario will now run 3 times, once for each IntegrationExample. You may access the example in the following way:

Given(
    'I access the example value',
    (tester, log, box, mocks, [example, binding]) {
      final int exampleValue = example!.firstValue();
    },
  )

💡

Be sure to make your declaration type safe so the firstValue() helper method can cast the value to whatever type your specify, use with caution!

🐾 Steps Implementation

Combining all that information will allow us to finalise and set up the success scenario like this:

class DummyIntegrationTest extends IntegrationTest {
  DummyIntegrationTest()
      : super(
          description: 'All integration tests regarding dummies',
          features: [
            IntegrationFeature(
              description: 'Saving of dummies',
              setUpOnce: (mocks) {
                final dummyMock = DummyMock();
                mocks.write(dummyMock);
              },
              scenarios: [
                IntegrationScenario(
                  description: 'Saving a good dummy should succeed',
                  steps: [
                    Given(
                      'The dummy service is initialised',
                      (tester, log, box, mocks, [example, binding]) {
                        mocks.read(DummyMock).stubWhatever();
                        // TODO(you): Initialise service
                      },
                    ),
                    When(
                      'We call the dummy service with dummy info',
                      (tester, log, box, mocks, [example, binding]) {
                        // TODO(you): Call dummy service with dummy info
                      },
                    ),
                    Then(
                      'It should succeed',
                      (tester, log, box, mocks, [example, binding]) {
                        // TODO(you): Verify success
                      },
                    ),
                  ],
                ),
                IntegrationScenario(
                  description: 'Saving a bad dummy should fail',
                  steps: [],
                ),
              ],
            ),
          ],
        );
}

💡

We have also added the usage of mocks in this example to demonstrate the IntegrationMocks feature. The IntegrationFeature now has a setupOnce method (more on this type of method later) that creates the mock and puts into the mocks object. We then later retrieve this mock in the Given step to stub it for a hypothetical reaction.

🏆 Bonus IntegrationSteps

Because not everybody wants to write tests the same way we also created these combined step classes to allow for creating the same kind of integration tests, but with less steps.

GivenWhenThen

For when you can’t be bothered to create and use the separate step functionality regarding the ‘Given’, ‘When’ and ‘Then’ steps. This allows you to write the entire test in one step.

WhenThen

For when you can’t be bothered to create and use the separate step functionality regarding the ‘When’ and ‘Then’ steps. This allows you to combine both steps into one.

Should

For when you feel like using steps is not your style. This step defines the entire test in one ‘Should’ sentence.

⚡️ Almost there!

While this may perfectly fit our testing needs there are a couple functionalities at our disposal that give our tests extra power.

🏗 setUpMocks, setUpOnce, setUpEach, tearDownOnce, tearDownEach

Each class has access to these methods and will run them in sort of the same way:

setUpMocks - will run first before any other method inside an IntegrationTest, IntegrationFeature or IntegrationScenario.
setUpEach - will run at the START of EACH IntegrationScenario under the chosen class (may be specified in IntegrationTest, IntegrationFeature or IntegrationScenario itself).
tearDownEach - will run at the END of EACH IntegrationScenario under the chosen class (may be specified in IntegrationTest, IntegrationFeature or IntegrationScenario itself).
setUpOnce - will run ONCE at the START of chosen class (may be specified in IntegrationTest, IntegrationFeature or IntegrationScenario itself).
tearDownOnce - will run ONCE at the END of chosen class (may be specified in IntegrationTest, IntegrationFeature or IntegrationScenario itself).

💡

So a good way to remember which method does what is that all the each methods will run per IntegrationScenario / IntegrationExample (this is important to realise!) under the defining class that holds the method and all the once methods will run once in the defining class that holds the method.

Using the methods may look a bit like this:

class DummyIntegrationTest extends IntegrationTest {
  DummyIntegrationTest()
      : super(
          description: 'All integration tests regarding dummies',
          features: [
            IntegrationFeature(
              description: 'Saving of dummies',
              setUpMocks: (mocks) {
                mocks.write(DummyMock());
              },
              setUpOnce: (mocks) {
                // Do something once
              },
              setUpEach: (mocks) async {
                AppSetup.reset();
              },
              tearDownOnce: (mocks) async {
                // Do something
              },
              scenarios: [
                IntegrationScenario(
                  description: 'Saving a good dummy should succeed',
                  steps: [
                    Given(
                      'The dummy service is initialised',
                      (tester, log, box, mocks, [example, binding]) {
                        mocks.read(DummyMock).stubWhatever();
                        // TODO(you): Initialise service
                      },
                    ),
                    When(
                      'We call the dummy service with dummy info',
                      (tester, log, box, mocks, [example, binding]) {
                        // TODO(you): Call dummy service with dummy info
                      },
                    ),
                    Then(
                      'It should succeed',
                      (tester, log, box, mocks, [example, binding]) {
                        // TODO(you): Verify success
                      },
                    ),
                  ],
                ),
                IntegrationScenario(
                  description: 'Saving a bad dummy should fail',
                  steps: [],
                ),
              ],
            ),
          ],
        );
}

Now to run these tests all you have to do is add the DummyIntegrationTests to your main test function and hit run. In this example we would like to use the IntegrationTestWidgetsFlutterBinding in our tests so let’s add that to the constructor as well.

// Adding it to the constructor
DummyIntegrationTest({required IntegrationTestWidgetsFlutterBinding binding})
      : super(
          description: 'All tests regarding dummies',
          binding: binding,

void main() {
// Getting the binding by calling this function
  final binding = IntegrationTestWidgetsFlutterBinding.ensureInitialized()
      as IntegrationTestWidgetsFlutterBinding;
// Running the test
  DummyIntegrationTests(binding: binding).test();
}