Automating Android Unit Tests with Xamarin
Recently, I’ve been evaluating Xamarin’s native bindings. As part of this, I started looking at how to run unit tests on real devices automatically as part of continuous integration (CI) builds. This is fairly well documented for iOS (see here). However, there is no similar documentation for Android. This post is an attempt to fill that gap. I’ll be using Xamarin Studio on Mac, but the steps should be similar if you’re using Visual Studio.
This post is about automated unit testing, as opposed to integration/acceptance testing. For details of running UI tests as part of an acceptance testing strategy, see Xamarin.UITest.
Creating the Project
With Xamarin Studio open, click File > New > Solution… and select Android Unit Test Project.
This will generate two source files, MainActivity.cs and TestsSample.cs. TestsSample.cs will look familiar if you’ve written NUnit tests before — it uses annotations to mark methods as tests and includes a number of examples. Under the covers Xamarin use NUnitLite for Android and iOS unit testing, which exposes the same annotations as NUnit and the same basic assertions. More information about the differences between NUnit and NUnitLite can be found here.
With MainActivity.cs, there are two interesting points. Firstly, it extends TestSuiteActivity.cs, which handles the execution of the tests. Secondly, the AddTest method is used to add tests to be executed from an assembly. The example passes in the currently executing assembly, but the tests could come from another referenced assembly.
Running this sample will show an activity with buttons for running the tests and changing some options. After running the tests, the results will be shown on screen.
Automating the Tests
We know how to run the tests manually, but how can we automate this? The documentation for unit testing on iOS points to the TouchRunner class. The documentation for this class shows that it’s quite simple to setup the iOS unit tests to be automated:
runner.Writer = new TcpTextWriter ("10.0.1.2", 16384);
// start running the test suites as soon as the application is loaded
runner.AutoStart = true;
// crash the application (to ensure it's ended) and return to springboard
runner.TerminateAfterExecution = true;
The AutoStart property of the runner is set to true to tell it to start running the tests once the configuration is complete. Setting the TerminateAfterExecution property to true ensures that the application does not stay running after the tests have been completed.
The final step is to actually get the results off of the device, which is where the Writer property comes in. The runner will write basic information about the device that it is running the tests on, as well the results of the tests, using the value of the Writer property. The default Writer writes the results to the console, but a TcpTextWriter is available that can send the results to a server.
Collecting the results and dealing with them is beyond the scope of this post, but a simple TCP server can be written in a few lines using Python that would be suitable for the job. A CI build just needs to start the server before executing the tests, ensuring that the unit test application knows the IP address and port for the TCP server.
The approach is not quite so straight forward on Android (the lack of documentation doesn’t help the matter). The first issue is that on Android there are no similar properties. The TestSuiteActivity only exposes a method for adding tests. When the application is running, we can see that there is an Options button which, when pressed, shows an activity that allows for setting the details of a remote server.
Setting these values to point to a TCP server and running the tests shows that the device details and test results are sent to the server. The code that is executing the tests has to be getting the host name and port somehow, so it’s time to start digging.
Right clicking TestSuiteActivity and clicking Go To Declaration results in the class being shown in the assembly browser. Setting language to C# in the top right-hand corner of the window shows a fairly readable version of the implementation. From the generated MainActiviy class, we can see that the work to start the execution of the tests must be happening in the OnCreate base method, so that seems like a good place to start:
protected override void OnCreate(Bundle bundle)
{
base.OnCreate (bundle);
...
bool booleanExtra = this.Intent.GetBooleanExtra ("automated", false);
if (booleanExtra) {
AndroidRunner.Runner.Options.LoadFromBundle (this.Intent.Extras);
}
...
if (booleanExtra) {
ThreadPool.QueueUserWorkItem (delegate {
Log.Info ("NUnitLite", "NUnit automated tests started");
AndroidRunner.Runner.Run (this.current_test, this);
Log.Info ("NUnitLite", "NUnit automated tests completed");
this.Finish ();
});
}
Log.Info ("NUnitLite", "NUnit automated tests loaded.");
}
Here we start to see some interesting stuff. The method gets a boolean extra from the intent called “automated”. This is then used to decide whether to load additional options from the extras. The value is used again later on to determine whether to automatically run the tests and finish the activity when the tests have completed, or wait for the user to manually run the tests. So, we know that adding a boolean called “automated” to the intent’s extras that is set to true will cause the tests to be automatically run. But how do we get the results to be sent to a waiting server? The key is in the AndroidRunner.Runner.Options.LoadFromBundle method:
public void LoadFromBundle(Bundle bundle)
{
this.EnableNetwork = bundle.GetBoolean ("remote", false);
this.HostName = (bundle.GetString ("hostName") ?? "0.0.0.0");
this.HostPort = bundle.GetInt ("hostPort", -1);
}
public bool ShowUseNetworkLogger
{
get
{
return this.EnableNetwork && !string.IsNullOrWhiteSpace (this.HostName) && this.HostPort > 0;
}
}
This provides the last piece of the puzzle. The host name and port are also pulled from the intent’s extras. The property ShowUseNetworkLogger, which is based on the “remote” extra, is used in AndroidRunner to determine whether to create a TcpTextWriter for writing the results, or just write to the console.
We can bring all this knowledge together in to a new class:
public abstract class AutomatedTestSuiteActivity : TestSuiteActivity
{
protected override void OnCreate(Bundle bundle)
{
Intent.PutExtra ("automated", true);
Intent.PutExtra ("remote", true);
Intent.PutExtra ("hostName", HostName);
Intent.PutExtra ("hostPort", HostPort);
base.OnCreate (bundle);
}
public override void Finish ()
{
System.Environment.Exit (0);
}
protected abstract string HostName { get; }
protected abstract int HostPort { get; }
}
This class now handles setting all the appropriate extras, all the extending class has to do is implement properties for the host name and port. Additionally, the Finish method has been overridden so that it forces the process to exit, ensuring that the application does not hang around after the tests have finished.
I hope that this post is useful to anyone else that is investigating automated Android unit tests with Xamarin and feel free to use the AutomatedTestSuiteActivity.
