Testable Android Architecture (Android Makers France)

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Testable Android Architecture 11 April 2017 / Chuck Greb / @ecgreb

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Clean code Software Craftsmanship

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The only thing that is constant is change. “ - Heraclitus ”

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Art is anything you can do well. Anything you can do with Quality. “ ” - Robert M. Pirsig

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→ MVC Model View Controller → MVP Model View Presenter → MVVM Model View ViewModel Clean Architecture Design patterns

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A brief history of Android development

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https://en.wikipedia.org/wiki/Android_version_history

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Activity

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Activity Activity Lifecycle System Services

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Activity EditText Button Activity Lifecycle System Services

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Activity EditText Button Web Service Storage AsyncTask Activity Lifecycle System Services

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Activity Fragment EditText Button Web Service Storage AsyncTask Activity Lifecycle System Services Fragment Fragment Lifecycle

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Fragment Activity EditText Button Web Service Storage AsyncTask Activity Lifecycle System Services Fragment Fragment Lifecycle User Input Input Validation

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Fragment Activity Web Service Storage AsyncTask Activity Lifecycle System Services Fragment Fragment Lifecycle User Input setRetainInstance(true) EditText Button Input Validation

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Fragment Activity Web Service Storage AsyncTask Activity Lifecycle System Services Fragment Fragment Lifecycle User Input setRetainInstance(true) Intent Parcelable Extras EditText Button Input Validation

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Web Service Storage Activity Fragment Fragment AsyncTask setRetainInstance(true) Activity Lifecycle Fragment Lifecycle System Services User Input Intent Test Case Parcelable Extras EditText Button Input Validation

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A cleaner approach...

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Activity Logic

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Activity Logic Data

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Activity Logic Data View

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- Phil Karlton There are only two hard problems in computer science: cache invalidation and naming things. “ ”

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View (Activity) Controller (Logic) Model (Data) View

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View (Activity) Presenter (Logic) Model (Data) View

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View (Activity) ViewModel (Logic) Model (Data) View

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Clean Architecture Model View Presenter Controller MVP(C)

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Controller (Activity) Presenter (Logic) Model (Data) View

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Activity Presenter (Logic) Model (Data) View Controller

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Web Service Storage Activity Activity Lifecycle System Services User Input Presenter View Model Controller Button EditText Thread Input Validation start()

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Web Service Storage Activity Activity Lifecycle System Services User Input Presenter View Model Controller Button EditText Input Validation Thread start()

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→ UI end-to-end tests through the user interface. Simulates actual usage of the app. Often slow, expensive, and brittle. → Service provide many of the advantages of end-to-end tests but avoid many of the complexities of dealing with UI frameworks. → Unit the smallest testable parts of an app are individually and independently exercised for proper operation. Test Pyramid

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If you get a failure in a high level test, not just do you have a bug in your functional code, you also have a missing or incorrect unit test. “ - Martin Fowler ”

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A test is not a unit test if: → It talks to the database → It communicates across the network → It touches the file system → It can't run at the same time as any of your other unit tests → You have to do special things to your environment (such as editing config files) to run it. Michael Feathers, 2005 Unit Test Rules

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→ UI end-to-end tests run on an emulator or device using the Espresso framework. → Integration using Robolectric tests can be run in the local JVM against the real Android JARs mocking only UI and system hardware components. → Unit use JUnit and Mockito plus a special mockable version of the Android JAR to test app code in isolation in the local JVM. Android Test Pyramid

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Test Types

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Unit Tests JUnit + Mockito (JVM)

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Mock Service Mock Storage Test Controller Presenter Model Controller JUnit TestRunner Thread run()

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Integration Tests Robolectric

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Activity Robolectric TestRunner Robolectric Runtime Environment Simulated Input View Button EditText Input Validation Mock Service Mock Storage Presenter Model Thread run()

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UI Tests Espresso

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Web Service Storage Activity Activity Lifecycle System Services Presenter View Model Controller Button EditText Thread Input Validation start() Android JUnit4 TestRunner

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→ Configuration Changes → View Presenters → Legacy Code FAQ Frequently Answered Questions

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Configuration Changes

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Web Service Storage Activity Activity Lifecycle System Services User Input Presenter View Model Controller Button EditText Thread Input Validation start()

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Web Service Storage Activity Activity Lifecycle System Services User Input Presenter View Model Controller Button EditText Thread Input Validation start() ViewState Manager (VSM)

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View Presenters

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View Model View Presenter Activity Activity Lifecycle System Services User Input Main Presenter View Controller Button EditText Input Validation Main Model

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Legacy Code

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→ Code that does not have tests was probably not written to be testable → Do not set aside dedicated time to “refactor” and “improve test coverage” → Test any new code that is added → Test any code around new code that is added → Use seams to break dependencies, decouple components, and modularize your code base Legacy Code Code without tests

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Demo App https://github.com/ecgreb/mvpc

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→ Clean architecture can help your code be more flexible, maintainable, and testable. → Choose an architecture appropriate to your use case. → Write unit, integration, and UI tests that work in concert with your architecture. → Don’t be overly dogmatic-- software development is an art and a science. Conclusion Which architecture and testing tools should I use?

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Merci à vous 11 April 2017 / Chuck Greb / @ecgreb