An Android app consuming a Star Wars API to display Movie Characters it has been built with clean architecture principles, Repository Pattern and MVVM pattern with unit testing.
The Application is split into a three layer architecture:
- Presentation
- Domain
- Data
This provides better abstractions between framework implementations and the underlying business logic.It requires a number of classes to get things running but the pros outweigh the cons in terms of building an app that should scale.
The 3 layered architectural approach is majorly guided by clean architecture which provides a clear separation of concerns with its Abstraction Principle.
app contains the UI files and handles binding of DI components from other modules.
Binding of data is facilitated by jetpacks data binding by serving data from the viewmodel
to the UI.The data being received is part of a viewstate class that has properties contained in the
relevant state.
The domain module contains domain model classes which represent the
data we will be handling across presentation and data layer.
Use cases are also provided in the domain layer and orchestrate the flow of data from the data layer onto the presentation layer and a split into modular pieces serving one particular purpose.
The UseCases use a BaseUseCase interface that defines the parameters its taking in and
output this helps in creating fakes using in testing.
data-remote
Handles data interacting with the network and is later serverd up to the presentation layer through domain object
data-local
Handles persistence of object with Room ORM from.This module is responsible for handling all local related logic and serves up data to and from the presentation layer through domain objects.
With this separation we can easily swap in new or replace the database being used without causeing major ripples across the codebase.
Each module has its own tests except for the domain module which is catered for since its
part of the behavior under test.
All server responses in the tests are served by mock web server by appending relative urls to the localhost and the connected port as the base url.
In the data-remote module the responses are mocked using the mockwebserver and verified that they
are what we expect.
In the data-local module an in memory database is being used to run the tests,this makes it a
little faster compared to an actual db.
In the app module there are unit tests for the viewmodels and util classes
and connected tests for the UI Screens.
The test instrumentation app uses modules that have been swaped with fakes for the network module so as to run requests on localhost with mockwebserver,this removes flakiness compared to relying on actual data from the real server aspects such as internet connection or network service might bring up issues and an in memory database for local data that also allows main thread queries since tests should also be fast and we are just asserting stuff works.
View models testing on live data were guided by this article
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