Unit Testing code built with MVVMCross SQLite Plugin - sqlite

Question

I'm currently building a Xamarin.Forms project using MVVMCross. In order to test my platform specific code I am using Nunit.Xamarin which features an app that run tests on device.
This test app is a forms app but doesn't use MVVMCross and I haven't had any luck setting it up to use MVVMCross due to the fact the Application class loads an App of type NUnit.Runner.App whereas MVVMCross requires MvxFormsApp.
I want to test this class the saves and loads user data from an SQLite Database:
public class DataStorageService : IDataStorageService
{
private readonly SQLiteConnection _connection;
public User UserData
{
get { return _connection.Table<User>().FirstOrDefault(); }
set { _connection.InsertOrReplace(value); }
}
public DataStorageService(IMvxSqliteConnectionFactory factory)
{
_connection = factory.GetConnection(DataStorageConstants.LocalDatabaseName);
_connection.CreateTable<User>();
}
}
I want to actually test that it saves and loads from a local SQLite database so I don't want to mock the IMvxSqliteConnectionFactory. I tried installing MVVMCross and the SQLite plugin into the project and then passing in the Android implementation of the connection factory but that repeatedly threw a typeloadexception.
Any ideas as to how I can set up this test with MVVMCross (or are there alternatives?) and dependency injection?

Answer 1

It is possible :) The important stuff happens in the MvxSplashScreenActivity. The MvxFormsApp is basically empty. So we don't have to care. Example Code: https://github.com/smstuebe/stackoverflow-answers/tree/master/mvx-android-test-app
Create a nunit Test app project
Install-Package MvvmCross.StarterPack -Version 4.1.4
Get rid of Views folder
Install the SQLite plugin
Reference your Core project
Install-Package MvvmCross.Forms.Presenter -Version 4.1.4
Remove MainLauncher = true from MainActivity
Adust Setup to return your core project's App
protected override IMvxApplication CreateApp()
{
return new MyApp.Core.App();
}
Change SplashScreen to (source)
[Activity(MainLauncher = true
, Theme = "#style/Theme.Splash"
, NoHistory = true
, ScreenOrientation = ScreenOrientation.Portrait)]
public class SplashScreen
: MvxSplashScreenActivity
{
public SplashScreen()
: base(Resource.Layout.SplashScreen)
{
}
private bool _isInitializationComplete;
public override void InitializationComplete()
{
if (!_isInitializationComplete)
{
_isInitializationComplete = true;
StartActivity(typeof(MainActivity));
}
}
protected override void OnCreate(Android.OS.Bundle bundle)
{
Forms.Init(this, bundle);
Forms.ViewInitialized += (object sender, ViewInitializedEventArgs e) =>
{
if (!string.IsNullOrWhiteSpace(e.View.StyleId))
{
e.NativeView.ContentDescription = e.View.StyleId;
}
};
base.OnCreate(bundle);
}
}
Write a test like
[TestFixture]
public class TestClass
{
[Test]
public void TestMethod()
{
var service = Mvx.Resolve<IDataStorageService>();
Assert.IsNull(service.UserData);
}
}
Enjoy the awesomeness of MvvmCross