Allow beans with circular dependencies to be spied

Closes gh-29639

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/mock/mockito/MockitoPostProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@ import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.springframework.aop.scope.ScopedProxyUtils;
 import org.springframework.beans.BeansException;
@@ -433,6 +434,8 @@ public class MockitoPostProcessor implements InstantiationAwareBeanPostProcessor
 
 		private static final String BEAN_NAME = SpyPostProcessor.class.getName();
 
+		private final Map<String, Object> earlySpyReferences = new ConcurrentHashMap<>(16);
+
 		private final MockitoPostProcessor mockitoPostProcessor;
 
 		SpyPostProcessor(MockitoPostProcessor mockitoPostProcessor) {
@@ -446,6 +449,10 @@ public class MockitoPostProcessor implements InstantiationAwareBeanPostProcessor
 
 		@Override
 		public Object getEarlyBeanReference(Object bean, String beanName) throws BeansException {
+			if (bean instanceof FactoryBean) {
+				return bean;
+			}
+			this.earlySpyReferences.put(getCacheKey(bean, beanName), bean);
 			return this.mockitoPostProcessor.createSpyIfNecessary(bean, beanName);
 		}
 
@@ -454,7 +461,14 @@ public class MockitoPostProcessor implements InstantiationAwareBeanPostProcessor
 			if (bean instanceof FactoryBean) {
 				return bean;
 			}
-			return this.mockitoPostProcessor.createSpyIfNecessary(bean, beanName);
+			if (this.earlySpyReferences.remove(getCacheKey(bean, beanName)) != bean) {
+				return this.mockitoPostProcessor.createSpyIfNecessary(bean, beanName);
+			}
+			return bean;
+		}
+
+		private String getCacheKey(Object bean, String beanName) {
+			return StringUtils.hasLength(beanName) ? beanName : bean.getClass().getName();
 		}
 
 		static void register(BeanDefinitionRegistry registry) {

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/mock/mockito/SpyBeanOnTestFieldForExistingCircularBeansIntegrationTests.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2012-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.test.mock.mockito;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.mock.mockito.SpyBeanOnTestFieldForExistingCircularBeansIntegrationTests.SpyBeanOnTestFieldForExistingCircularBeansConfig;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import static org.mockito.BDDMockito.then;
+
+/**
+ * Test {@link SpyBean @SpyBean} on a test class field can be used to replace existing
+ * beans with circular dependencies.
+ *
+ * @author Andy Wilkinson
+ */
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration(classes = SpyBeanOnTestFieldForExistingCircularBeansConfig.class)
+class SpyBeanOnTestFieldForExistingCircularBeansIntegrationTests {
+
+	@SpyBean
+	private One one;
+
+	@Autowired
+	private Two two;
+
+	@Test
+	void beanWithCircularDependenciesCanBeSpied() {
+		this.two.callOne();
+		then(this.one).should().someMethod();
+	}
+
+	@Import({ One.class, Two.class })
+	static class SpyBeanOnTestFieldForExistingCircularBeansConfig {
+
+	}
+
+	static class One {
+
+		@Autowired
+		@SuppressWarnings("unused")
+		private Two two;
+
+		void someMethod() {
+
+		}
+
+	}
+
+	static class Two {
+
+		@Autowired
+		private One one;
+
+		void callOne() {
+			this.one.someMethod();
+		}
+
+	}
+
+}