QuarkusComponentTest: class loading refactoring #50164

mkouba · 2025-09-19T11:27:38Z

resolves QuarkusComponentTest: support simplified constructor injection #43339

The goal of this pull request is to refactor the class loading used for QuarkusComponentTest, i .e. use a transformation-aware class loader to load a test class annotated with @QuarkusComponentTest. This way we can support things like simplified constructor injection.

Implementation-wise - we hook into the FacaClassLoader logic (if present) and similarly to how @QuarkusTest is handled, we build the container (ArC in case of QuarkusComponentTest) when the test classes are loaded (note that there must be a special handling for continuous testing where io.quarkus.deployment.dev.testing.JunitTestRunner is used to load the test classes).

When I discussed this PR with Ladislav and Matej, we had an idea that quarkus-junit5 and quarkus-junit5-component could be merged in one artifact. However, it turns out we would have to add a bunch of dependencies to quarkus-junit5 (including ArC, but what's worse also Mockito + bytebuddy - this combo has ~ 4MB of jars). So I decided to introduce the io.quarkus.test.common.FacadeClassLoaders SPI instead. It lives in the quarkus-test-common and the name is terrible, but it works soo 🤷.

There's one use case where the new approach fails. It's a QuarkusDevModeTest iff quarkus-junit5 is not present, something along the lines of https://github.com/quarkusio/quarkus/blob/main/integration-tests/devmode/src/test/java/io/quarkus/test/component/ComponentContinuousTestingTest.java. I found that quarkus-junit5 provides QuarkusTestConfigProviderResolver that somehow overrides io.quarkus.test.config.TestConfigProviderResolver to avoid Context ClassLoader mismatch. But I have no idea why/how and why TestConfigProviderResolver exists for the first place.

This change should not break any existing apps but the test coverage is limited..

...unit5-component/src/main/java/io/quarkus/test/component/QuarkusComponentTestClassLoader.java

Ladicek · 2025-09-22T11:39:36Z

When I discussed this PR with Ladislav and Matej, we had an idea that quarkus-junit5 and quarkus-junit5-component could be merged in one artifact. However, it turns out we would have to add a bunch of dependencies to quarkus-junit5 (including ArC, but what's worse also Mockito + bytebuddy - this combo has ~ 4MB of jars). So I decided to introduce the io.quarkus.test.common.FacadeClassLoaders SPI instead. It lives in the quarkus-test-common and the name is terrible, but it works soo 🤷.

Not an expert, but could we maybe move the whole infrastructure to quarkus-test-common? (By infrastructure, I mean CustomLauncherInterceptor, FacadeClassLoader, the SPI you added here and maybe a few other classes.) This would require quarkus-test-common to actually depend on junit-jupiter, which doesn't necessarily have to be a problem, and it would let us ditch ComponentLauncherSessionListener. We would always have the same one present. The SPI you added here (FacadeClassLoaders) should be renamed (:laughing:) and provide at least some notion of lifecycle (to allow cleaning up at the end). Again, not an expert, perhaps that doesn't make much sense.

Also, I'm not sure I'm able to do a proper review here, certainly not without playing with this locally for a while :-)

mkouba · 2025-09-22T12:02:40Z

When I discussed this PR with Ladislav and Matej, we had an idea that quarkus-junit5 and quarkus-junit5-component could be merged in one artifact. However, it turns out we would have to add a bunch of dependencies to quarkus-junit5 (including ArC, but what's worse also Mockito + bytebuddy - this combo has ~ 4MB of jars). So I decided to introduce the io.quarkus.test.common.FacadeClassLoaders SPI instead. It lives in the quarkus-test-common and the name is terrible, but it works soo 🤷.

Not an expert, but could we maybe move the whole infrastructure to quarkus-test-common? (By infrastructure, I mean CustomLauncherInterceptor, FacadeClassLoader, the SPI you added here and maybe a few other classes.) This would require quarkus-test-common to actually depend on junit-jupiter, which doesn't necessarily have to be a problem, and it would let us ditch ComponentLauncherSessionListener. We would always have the same one present.

I'm not an expert either but I don't feel confident enough to do such a bold move. Also FaceClassLoader depends on many other classes from the quarkus-junit such as io.quarkus.test.junit.AppMakerHelper and I'm not really sure it will be that easy to move them without breaking stuff.

The SPI you added here (FacadeClassLoaders) should be renamed (:laughing:) and provide at least some notion of lifecycle (to allow cleaning up at the end). Again, not an expert, perhaps that doesn't make much sense.

Right now, I think that we don't need any cleanup... which doesn't mean we won't need it in the future but I'd like to keep the SPI minimal. If possible, it should be considered internal. But AFAIK the only thing we could do is to add a sentence in the javadoc.

Speaking of the name - do you have a better idea? Because I'm out of ideas...

Also, I'm not sure I'm able to do a proper review here, certainly not without playing with this locally for a while :-)

No problem. Your feeedback is really appreciated! 🙏

Ladicek · 2025-09-22T12:10:14Z

I'm not an expert either but I don't feel confident enough to do such a bold move. Also FaceClassLoader depends on many other classes from the quarkus-junit such as io.quarkus.test.junit.AppMakerHelper and I'm not really sure it will be that easy to move them without breaking stuff.

Makes sense.

The SPI you added here (FacadeClassLoaders) should be renamed (:laughing:) and provide at least some notion of lifecycle (to allow cleaning up at the end). Again, not an expert, perhaps that doesn't make much sense.

Right now, I think that we don't need any cleanup... which doesn't mean we won't need it in the future but I'd like to keep the SPI minimal. If possible, it should be considered internal. But AFAIK the only thing we could do is to add a sentence in the javadoc.

👍

Speaking of the name - do you have a better idea? Because I'm out of ideas...

Nothing extraordinary. I'd just call it FacadeClassLoaderProvider or something.

manovotn · 2025-09-23T09:36:28Z

I am going through the code now but in the meantime - I was thinking whether it would be worth adding a note to the documentation stating that component tests now support transformations?

mkouba · 2025-09-23T13:51:53Z

I am going through the code now but in the meantime - I was thinking whether it would be worth adding a note to the documentation stating that component tests now support transformations?

Once we merge this pull request I'd like to write a blog post that would mention all recent improvements (incl. @InjectMock Event). Basically a follow-up of https://quarkus.io/blog/quarkus-component-test/. Speaking of the docs - we didn't mention it does not work so I'm not really sure it's important 🤷.

manovotn · 2025-09-23T15:37:51Z

I am going through the code now but in the meantime - I was thinking whether it would be worth adding a note to the documentation stating that component tests now support transformations?

Once we merge this pull request I'd like to write a blog post that would mention all recent improvements (incl. @InjectMock Event). Basically a follow-up of https://quarkus.io/blog/quarkus-component-test/.

That's great idea! 👍

Speaking of the docs - we didn't mention it does not work so I'm not really sure it's important 🤷.

I know, but fair enough.
My thinking was that users might have encountered this shortcoming before and gave up on using the extension; I was just looking for a way to rise awareness. I suppose a blogpost would work just as well :)

mkouba · 2025-09-24T07:14:08Z

BTW I think that this would open the door to other possibilities. For example, we could try to add support Panache mocking for the active record pattern.

manovotn

Added a few comments and questions.
Take them with a pinch of salt as while I understand what the PR does, I certainly do have hard time understanding how exactly with all the class loader juggling :)

test-framework/junit5/src/main/java/io/quarkus/test/junit/classloading/FacadeClassLoader.java

test-framework/common/src/main/java/io/quarkus/test/common/FacadeClassLoaderProvider.java

test-framework/junit5-component/src/main/java/io/quarkus/test/component/ComponentContainer.java

...nit5-component/src/main/java/io/quarkus/test/component/ComponentLauncherSessionListener.java

mkouba · 2025-09-24T12:32:32Z

Added a few comments and questions. Take them with a pinch of salt as while I understand what the PR does, I certainly do have hard time understanding how exactly with all the class loader juggling :)

Totally understand, it took me a few days to understand at least part of the class loading code...

- resolves quarkusio#43339

quarkus-bot · 2025-09-25T14:23:05Z

Status for workflow `Quarkus CI`

This is the status report for running Quarkus CI on commit e88c55f.

✅ The latest workflow run for the pull request has completed successfully.

It should be safe to merge provided you have a look at the other checks in the summary.

You can consult the Develocity build scans.

Flaky tests - Develocity

⚙️ JVM Tests - JDK 17

📦 extensions/smallrye-reactive-messaging/deployment

❌ io.quarkus.smallrye.reactivemessaging.hotreload.ConnectorChangeTest.testUpdatingConnector - History

Expecting actual: ["-4","-5","-6","-7","-8","-9","-10","-11"] to start with: ["-3", "-4", "-5", "-6"] - java.lang.AssertionError

java.lang.AssertionError: 

Expecting actual:
  ["-4","-5","-6","-7","-8","-9","-10","-11"]
to start with:
  ["-3", "-4", "-5", "-6"]

	at io.quarkus.smallrye.reactivemessaging.hotreload.ConnectorChangeTest.testUpdatingConnector(ConnectorChangeTest.java:36)

⚙️ JVM Tests - JDK 21

📦 extensions/smallrye-openapi/deployment

❌ io.quarkus.smallrye.openapi.test.vertx.OpenApiHttpRootPathCorsTestCase.testCorsFilterProperties - History

1 expectation failed. Expected status code <200> but was <500>. - java.lang.AssertionError

java.lang.AssertionError: 
1 expectation failed.
Expected status code <200> but was <500>.

	at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:62)
	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:502)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:486)
	at org.codehaus.groovy.reflection.CachedConstructor.invoke(CachedConstructor.java:73)

⚙️ Maven Tests - JDK 17

📦 integration-tests/devmode

❌ io.quarkus.test.devui.DevUIGrpcSmokeTest.testTestService - History

Too many recursions, message not returned for id [1184811301] - java.lang.RuntimeException

java.lang.RuntimeException: Too many recursions, message not returned for id [1184811301]
	at io.quarkus.devui.tests.DevUIJsonRPCTest.objectResultFromJsonRPC(DevUIJsonRPCTest.java:175)
	at io.quarkus.devui.tests.DevUIJsonRPCTest.objectResultFromJsonRPC(DevUIJsonRPCTest.java:178)
	at io.quarkus.devui.tests.DevUIJsonRPCTest.objectResultFromJsonRPC(DevUIJsonRPCTest.java:178)
	at io.quarkus.devui.tests.DevUIJsonRPCTest.objectResultFromJsonRPC(DevUIJsonRPCTest.java:178)
	at io.quarkus.devui.tests.DevUIJsonRPCTest.objectResultFromJsonRPC(DevUIJsonRPCTest.java:178)
	at io.quarkus.devui.tests.DevUIJsonRPCTest.objectResultFromJsonRPC(DevUIJsonRPCTest.java:178)
	at io.quarkus.devui.tests.DevUIJsonRPCTest.objectResultFromJsonRPC(DevUIJsonRPCTest.java:178)

⚙️ Gradle Tests - JDK 17

📦 integration-tests/gradle

❌ io.quarkus.gradle.TestFixturesClientExceptionMapperTest.testBasicMultiModuleBuild - History

Gradle build failed with exit code 1 - java.lang.AssertionError

java.lang.AssertionError: Gradle build failed with exit code 1
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:173)
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:87)
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:82)
	at io.quarkus.gradle.TestFixturesClientExceptionMapperTest.testBasicMultiModuleBuild(TestFixturesClientExceptionMapperTest.java:12)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

Gradle build failed with exit code 1 - java.lang.AssertionError

java.lang.AssertionError: Gradle build failed with exit code 1
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:173)
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:87)
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:82)
	at io.quarkus.gradle.TestFixturesClientExceptionMapperTest.testBasicMultiModuleBuild(TestFixturesClientExceptionMapperTest.java:12)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

Gradle build failed with exit code 1 - java.lang.AssertionError

java.lang.AssertionError: Gradle build failed with exit code 1
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:173)
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:87)
	at io.quarkus.gradle.QuarkusGradleWrapperTestBase.runGradleWrapper(QuarkusGradleWrapperTestBase.java:82)
	at io.quarkus.gradle.TestFixturesClientExceptionMapperTest.testBasicMultiModuleBuild(TestFixturesClientExceptionMapperTest.java:12)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

mkouba · 2025-09-29T06:26:41Z

@Ladicek @manovotn @holly-cummins I'd like to merge this pull request today. It's not perfect but we could address potential issues in the follow ups. I already have a POC for extension points called QuarkusComponentTestCallbacks and integration with quarkus-panache-mock that makes it possible to mock Panache entitites in a QuarkusComponentTest.

core/deployment/src/main/java/io/quarkus/deployment/dev/testing/JunitTestRunner.java

holly-cummins · 2025-09-29T11:20:57Z

...unit5-component/src/main/java/io/quarkus/test/component/QuarkusComponentTestClassLoader.java

+    private static boolean mustDelegateToParent(String name) {
+        return name.startsWith("java.")
+                || name.startsWith("jdk.")
+                || name.startsWith("javax.")
+                || name.startsWith("jakarta.")
+                || name.startsWith("sun.")
+                || name.startsWith("com.sun.")
+                || name.startsWith("org.w3c.")
+                || name.startsWith("org.xml.")
+                || name.startsWith("org.junit.")
+                || name.startsWith("org.mockito.")
+                || PARENT_CL_CLASSES.contains(name);


Is there any way to get this code more common with the QuarkusClassLoader? I seem to recall doing a few hacky overrides to what gets loaded parent-first over there to support dev services work. It might be (a) less code and (b) fewer confusing bugs if we had a common service.

I'm not sure TBH. But I admit that this does not look very smart (it's more or less a result of experimentation) and we should get back to that sometime.

The list here looks quite close to what I had in #35473 and that wasn't a result of experimentation -- that was a list of packages provided by the JDK. There's a few packages added here (jakarta.*, org.junit.*, org.mockito.*) which make perfect sense, but still -- it's a list of packages we know are never provided by the application and make no sense to be loaded by the application class loader.

it's a list of packages we know are never provided by the application and make no sense to be loaded by the application class loader.

On the other hand, I observed weird errors while adding other packages which are also never provided by the app 🤷.

Well, that sounds strange then.

quarkus-bot bot added area/core area/testing labels Sep 19, 2025

mkouba force-pushed the component-classloading branch from d3a8aa5 to e84c5c4 Compare September 19, 2025 12:12

mkouba requested review from Ladicek, gsmet, manovotn and holly-cummins September 19, 2025 12:45

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QuarkusComponentTest: class loading refactoring

e88c55f

- resolves quarkusio#43339

mkouba force-pushed the component-classloading branch from 2ba3a7d to e88c55f Compare September 25, 2025 10:25

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mkouba merged commit e5167c6 into quarkusio:main Sep 29, 2025
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QuarkusComponentTest: introduce QuarkusComponentTestCallbacks, integrate seamlessly with quarkus-panache-mock #50323

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QuarkusComponentTest: class loading refactoring #50164

QuarkusComponentTest: class loading refactoring #50164

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⚙️ JVM Tests - JDK 17

📦 extensions/smallrye-reactive-messaging/deployment

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