Allow @MockBean to be used with Framework's @Repeat

Fixes gh-27693

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -355,9 +355,13 @@ public class MockitoPostProcessor implements InstantiationAwareBeanPostProcessor
 	private void inject(Field field, Object target, String beanName) {
 		try {
 			field.setAccessible(true);
-			Assert.state(ReflectionUtils.getField(field, target) == null,
+			Object existingValue = ReflectionUtils.getField(field, target);
-					() -> "The field " + field + " cannot have an existing value");
 			Object bean = this.beanFactory.getBean(beanName, field.getType());
+			if (existingValue == bean) {
+				return;
+			}
+			Assert.state(existingValue == null, () -> "The existing value '" + existingValue + "' of field '" + field
+					+ "' is not the same as the new value '" + bean + "'");
 			ReflectionUtils.setField(field, target, bean);
 		}
 		catch (Throwable ex) {

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/mock/mockito/MockBeanWithSpringMethodRuleRepeatJUnit4IntegrationTests.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2012-2021 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.AfterClass;
+import org.junit.Rule;
+import org.junit.Test;
+
+import org.springframework.test.annotation.Repeat;
+import org.springframework.test.context.junit4.rules.SpringMethodRule;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link MockBean} and {@link Repeat}.
+ *
+ * @author Andy Wilkinson
+ * @see <a href="https://github.com/spring-projects/spring-boot/issues/27693">gh-27693</a>
+ */
+public class MockBeanWithSpringMethodRuleRepeatJUnit4IntegrationTests {
+
+	@Rule
+	public final SpringMethodRule springMethodRule = new SpringMethodRule();
+
+	@MockBean
+	private FirstService first;
+
+	private static int invocations;
+
+	@AfterClass
+	public static void afterClass() {
+		assertThat(invocations).isEqualTo(2);
+	}
+
+	@Test
+	@Repeat(2)
+	public void repeatedTest() {
+		invocations++;
+	}
+
+	interface FirstService {
+
+		String greeting();
+
+	}
+
+}

src/checkstyle/checkstyle-suppressions.xml

@@ -40,6 +40,7 @@
 	<suppress files="SampleLogbackApplication\.java" checks="IllegalImport" />
 	<suppress files="FlywayAutoConfigurationTests\.java" checks="IllegalImport" />
 	<suppress files="[\\/]src[\\/]test[\\/]java[\\/]org[\\/]springframework[\\/]boot[\\/]test[\\/]rule[\\/]" checks="SpringJUnit5" />
+	<suppress files="MockBeanWithSpringMethodRuleRepeatJUnit4IntegrationTests" checks="SpringJUnit5" />
 	<suppress files="OutputCaptureRuleTests" checks="SpringJUnit5" />
 	<suppress files="SampleJUnitVintageApplicationTests" checks="SpringJUnit5" />
 	<suppress files="[\\/]spring-boot-docs[\\/]" checks="SpringJavadoc" message="\@since" />