Reset JUNIT5 MockBeans in BeforeEach

ResetAllMocksInContextExtension.kt

class ResetAllMocksInContextExtension : BeforeEachCallback {

    override fun beforeEach(context: ExtensionContext?) {

        val testInstance = context!!.testInstance.get()
        val testContext = getAccessibleContext(testInstance)
        resetMocksInContext(testContext)
    }

    private fun getAccessibleContext(testInstance: Any): Any? {
        // Within the test instance is a private context that we need to access, so we are setting the field as accessible on the class
        val contextFieldDefinition = testInstance::class.java.declaredFields[0]
        contextFieldDefinition.isAccessible = true

        return contextFieldDefinition.get(testInstance)
    }

    private fun resetMocksInContext(testContext: Any?) {
        testContext!!::class.java.declaredFields
                .mapNotNull { fieldDefinition -> getAccessibleField(fieldDefinition, testContext) }
                .filter { property -> isMock(property) }
                .forEach { mock -> reset(mock) }
    }

    private fun getAccessibleField(fieldDefinition: Field, testContext: Any?): Any? {
        fieldDefinition.isAccessible = true
        return fieldDefinition.get(testContext)
    }

    private fun isMock(property: Any) = property::class.java.declaredFields.find { field -> field.name == "mockitoInterceptor" } != null
}

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@ExtendWith(SpringExtension::class, ResetAllMocksInContextExtension::class)
@SpringBootTest
@ActiveProfiles("test")
annotation class RestControllerTest

----------------------------

@RestControllerTest
class ControllerTest {
    ...
}