Lombok generated constructor can not implicit autowire in SpringBootTest

I want to inject class A into class B through the constructor.

Class Structure in test directory

@Component
public class A {
}

import lombok.RequiredArgsConstructor;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
@RequiredArgsConstructor
public class B {
    private final A a;

    @Test
    public void testB() {
        System.out.println("testB");
    }
}

But the following error is thrown when I run the test.

org.junit.jupiter.api.extension.ParameterResolutionException: No ParameterResolver registered for parameter [final com.wen.h2.A a] in constructor [public com.wen.h2.B(com.wen.h2.A)].
    at org.junit.jupiter.engine.execution.ExecutableInvoker.resolveParameter(ExecutableInvoker.java:200)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.resolveParameters(ExecutableInvoker.java:183)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:74)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestClassConstructor(ClassBasedTestDescriptor.java:342)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateTestClass(ClassBasedTestDescriptor.java:289)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.instantiateTestClass(ClassTestDescriptor.java:79)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateAndPostProcessTestInstance(ClassBasedTestDescriptor.java:267)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$2(ClassBasedTestDescriptor.java:259)
    at java.util.Optional.orElseGet(Optional.java:267)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$3(ClassBasedTestDescriptor.java:258)
    at org.junit.jupiter.engine.execution.TestInstancesProvider.getTestInstances(TestInstancesProvider.java:31)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$prepare$0(TestMethodTestDescriptor.java:101)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:100)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$prepare$1(NodeTestTask.java:111)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.prepare(NodeTestTask.java:111)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:79)
    at java.util.ArrayList.forEach(ArrayList.java:1259)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.util.ArrayList.forEach(ArrayList.java:1259)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:221)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)

Answer

The problem is already raised in issue#22286, due to difference in autowire handling between Spring and Spring integration with JUnit. Which failed to do implicit autowire on constructor without @Autowired.

So as a workaround, add onConstructor = @__(@Autowired) to @RequiredArgsConstructor to annotate the generated constructor with @Autowired.

@SpringBootTest
@RequiredArgsConstructor(onConstructor = @__(@Autowired))
public class B {
    private final A a;
...
}

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Answer