13. Domain reload

Learning objectives

In this section, you will learn how to invoke and wait for Domain Reloads.

Intro and motivation

When performing actions that affect the scripts in a project, Unity performs a domain reload. Since a domain reload restarts all scripts, then it's necessary to mark any expected domain reload by yielding a WaitForDomainReload. The command stops any further code execution and then resumes after the domain reload is done.

It's also possible to yield a RecompileScripts command. This does the same as WaitForDomainReload except that it performs an AssetDatabase.Reload() call. Both calls can be configured to expect whether a script compilation is expected to succeed.

If a domain reload happens while a test is running without yielding one of these commands, then the test will fail with an error about an unexpected domain reload.

Exercise

The sample 13_DomainReload_Solution is set up with a test class called ScriptAddingTests.

The test has two helper methods already implemented:

CreateScript creates a C# script with a class called MyTempScript. That has a method called Verify.
VerifyScript instantiates an instance of MyTempScript using reflection and returns the value from the Verify method. The expected return value is the string "OK".

After running CreateScript Unity now has a new C# file in the project and thus needs to recompile. The task is to create a test that calls CreateScript, handles the domain reload and then verifies the output from VerifyScript.

Remember that your script should also clean up after itself, by deleting the file and recompiling the script again. This is recommended to do in a TearDown or UnityTearDown, which will run even if the test fails.

Hints

If RecompileScripts is unavailable to you due to it being internal, then you need to upgrade the Unity Test Framework package to version 1.1.0 or higher.
If you are on a non-Windows machine you might want to change paths inside k_fileName or use C# Path.Combine for more cross-platform safe code.

Solution

A full solution is available in the sample 13_DomainReload_Solution.

The test can be implemented as follows:

internal class ScriptAddingTests
{
 private const string k_fileName = @"Assets\\Tests\\TempScript.cs";
 
 [UnityTest]
 public IEnumerator CreatedScriptIsVerified()
 {
  CreateScript();
  yield return new RecompileScripts();

  var verification = VerifyScript();
  
  Assert.That(verification, Is.EqualTo("OK"));
 }

 [UnityTearDown]
 public IEnumerator Teardown()
 {
  if (!File.Exists(k_fileName))
  {
   yield break;
  }
  
  File.Delete(k_fileName);
  yield return new RecompileScripts();
 }
 
 private void CreateScript()
 {
  File.WriteAllText(k_fileName, @"
  public class MyTempScript {
   public string Verify()
   {
    return ""OK"";
   } 
  }");
 }

 private string VerifyScript()
 {
  Type type = Type.GetType("MyTempScript", true);
  
  object instance = Activator.CreateInstance(type);

  var verifyMethod = type.GetMethod("Verify", BindingFlags.Instance | BindingFlags.Public);

  var verifyResult = verifyMethod.Invoke(instance, new object[0]);
  return verifyResult as string;
 }
}