Duplicate BeanOverrideHandler discovered in @Nested test class hierarchy when upgrading to Spring 6.2.2

[bwaldvogel]

Consider the following test with nested test classes:

@SpringBootTest
class SomeTest {

    @MockitoSpyBean
    SomeService someService;

    abstract class BaseClassForNestedTests {
        @Test
        void someTest() {}
    }

    @Nested
    class SomeNestedTest extends BaseClassForNestedTests {}
}

@Service
class SomeService {
}

When upgrading Spring Boot 3.4.1 to 3.4.2 (which upgrades Spring from 6.2.1 to 6.2.2), the test starts to fail with:

Duplicate BeanOverrideHandler discovered in test class SomeTest$SomeNestedTest: [MockitoSpyBeanOverrideHandler@5c48c0c0 field = SomeService SomeTest.someService, beanType = SomeService, beanName = [null], strategy = WRAP, reset = AFTER]
java.lang.IllegalStateException: Duplicate BeanOverrideHandler discovered in test class SomeTest$SomeNestedTest: [MockitoSpyBeanOverrideHandler@5c48c0c0 field = SomeService SomeTest.someService, beanType = SomeService, beanName = [null], strategy = WRAP, reset = AFTER]
	at org.springframework.util.Assert.state(Assert.java:101)
	at org.springframework.test.context.bean.override.BeanOverrideContextCustomizerFactory.lambda$findBeanOverrideHandlers$1(BeanOverrideContextCustomizerFactory.java:55)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at org.springframework.test.context.bean.override.BeanOverrideContextCustomizerFactory.findBeanOverrideHandlers(BeanOverrideContextCustomizerFactory.java:54)
	at org.springframework.test.context.bean.override.BeanOverrideContextCustomizerFactory.createContextCustomizer(BeanOverrideContextCustomizerFactory.java:46)
	at org.springframework.test.context.bean.override.BeanOverrideContextCustomizerFactory.createContextCustomizer(BeanOverrideContextCustomizerFactory.java:38)
	at org.springframework.test.context.support.AbstractTestContextBootstrapper.getContextCustomizers(AbstractTestContextBootstrapper.java:360)
	at org.springframework.test.context.support.AbstractTestContextBootstrapper.buildMergedContextConfiguration(AbstractTestContextBootstrapper.java:332)
	at org.springframework.test.context.support.AbstractTestContextBootstrapper.buildDefaultMergedContextConfiguration(AbstractTestContextBootstrapper.java:267)
	at org.springframework.test.context.support.AbstractTestContextBootstrapper.buildMergedContextConfiguration(AbstractTestContextBootstrapper.java:215)
	at org.springframework.test.context.support.AbstractTestContextBootstrapper.buildTestContext(AbstractTestContextBootstrapper.java:108)
	at org.springframework.boot.test.context.SpringBootTestContextBootstrapper.buildTestContext(SpringBootTestContextBootstrapper.java:111)
	at org.springframework.test.context.TestContextManager.<init>(TestContextManager.java:142)
	at org.springframework.test.context.TestContextManager.<init>(TestContextManager.java:126)
	at org.springframework.test.context.junit.jupiter.SpringExtension.getTestContextManager(SpringExtension.java:363)
	at org.springframework.test.context.junit.jupiter.SpringExtension.beforeAll(SpringExtension.java:128)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)

I tried to do a search to find if this issue was already reported. I found #34204 which could be related to this issue.

[sbrannen]

What happens if you declare BaseClassForNestedTests as a static nested class or as a stand-alone top-level class?

[sbrannen]

Similarly, what happens if you annotate your non-static nested base class with @NestedTestConfiguration, as follows?

@NestedTestConfiguration(EnclosingConfiguration.OVERRIDE)
abstract class BaseClassForNestedTests {
	// ...
}

Alternatively, you should be able to annotate SomeNestedTest with @NestedTestConfiguration(EnclosingConfiguration.OVERRIDE) to achieve the same effect.

[sbrannen]

I tried to do a search to find if this issue was already reported. I found #34204 which could be related to this issue.

The change in behavior that you have reported is not related to #34204 but rather results from the changes made to BeanOverrideContextCustomizerFactory and BeanOverrideHandler in conjunction with #33925 (see commit 9181cce for details).

[bwaldvogel]

What happens if you declare BaseClassForNestedTests as a static nested class or as a stand-alone top-level class?

This would work, however, in my real-world case I cannot make the base class static.

Similarly, what happens if you annotate your non-static nested base class with @NestedTestConfiguration, as follows?

@NestedTestConfiguration(EnclosingConfiguration.OVERRIDE)
abstract class BaseClassForNestedTests {
	// ...
}

This fixes the error.

[sbrannen]

This fixes the error.

Thanks for confirming that @NestedTestConfiguration allows you to address that scenario.

In light of that, I am closing this issue as "works as designed".

Cheers,

Sam

[bwaldvogel]

Oh, I’m actually surprised to be honest and thought that this behavior change will be addressed. I think from a developer point of view it will be quite surprising and I’m sure that many developers will not know why the exception occurs and how to fix it (i.e. adding the @NestedTestConfiguration(EnclosingConfiguration.OVERRIDE) at the right place).

[sbrannen]

Thanks for the feedback, @bwaldvogel.

Although the current behavior (introduced in 6.2.2) may be considered technically correct in terms of the search algorithm, it is also technically a "regression" in behavior for test bean overrides, and as you mentioned, users may not find it readily apparent how an enclosing class can be visited twice by the search algorithm.

In light of that, I am reopening this issue with the plan to not search in the enclosing class hierarchy of a supertype of a @Nested test class, which should allow your original use case to work without modification.

[aykborstelmann]

We stumbled across a circumstance for which the problem is still there. Do you want me to open a new issue or should we discuss it here ?

[sbrannen]

@aykborstelmann, if you have discovered a bug that is still present in Spring Framework 6.2.6, please open a new issue with a reproducer.

Thanks

[aykborstelmann]

Alright, done in #34844.