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Unity Engine

13. Domain reload

Invoke and wait for domain reload from your tests.
Read time 2 minutesLast updated 22 days ago

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.
Important
After importing, you should move the sample test folder 
Tests_13
into the 
Assets
folder for this exercise to work.

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; }}

Additional resources

API reference for 
RecompileScripts
API reference for 
WaitForDomainReload