Register AutoConfigurations using fully qualified class name

Update `AbstractApplicationContextRunner` and `Configurations` to
allow registration of beans with a specific generated bean name. By
default, no name is generated, however, `AutoConfigurations` has been
updated to use bean names using the fully qualified class name.

The update brings `ApplicationContextRunners` closer the behavior of
a standard Spring Boot application where user `@Configuration` classes
are usually registered with a simple name and auto-configurations are
imported (via an `ImportSelector`) using a fully qualified name.

Fixes gh-17963

Co-authored-by: Stéphane Nicoll <stephane.nicoll@broadcom.com>
Co-authored-by: Andy Wilkinson <andy.wilkinson@broadcom.com>
Co-authored-by: Dmytro Nosan <dimanosan@gmail.com>

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/example/duplicate/first/EmptyConfig.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2024 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.context.example.duplicate.first;
+
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * Example configuration to showcase handing of duplicate class names.
+ *
+ * @author Stephane Nicoll
+ */
+@Configuration
+public class EmptyConfig {
+
+}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/example/duplicate/second/EmptyConfig.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2024 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.context.example.duplicate.second;
+
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * Example configuration to showcase handing of duplicate class names.
+ *
+ * @author Stephane Nicoll
+ */
+@Configuration
+public class EmptyConfig {
+
+}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunnerTests.java

@@ -17,6 +17,9 @@
 package org.springframework.boot.test.context.runner;
 
 import java.io.IOException;
+import java.util.Collection;
+import java.util.List;
+import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -27,6 +30,8 @@ import org.springframework.beans.factory.BeanCurrentlyInCreationException;
 import org.springframework.beans.factory.BeanDefinitionStoreException;
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.support.BeanDefinitionOverrideException;
+import org.springframework.boot.context.annotation.Configurations;
 import org.springframework.boot.context.annotation.UserConfigurations;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
@@ -139,6 +144,38 @@ abstract class AbstractApplicationContextRunnerTests<T extends AbstractApplicati
 		get().withUserConfiguration(FooConfig.class).run((context) -> assertThat(context).hasBean("foo"));
 	}
 
+	@Test
+	void runWithUserConfigurationsRegistersDefaultBeanName() {
+		get().withUserConfiguration(FooConfig.class)
+			.run((context) -> assertThat(context).hasBean("abstractApplicationContextRunnerTests.FooConfig"));
+	}
+
+	@Test
+	void runWithUserConfigurationsWhenHasSameShortClassNamedRegistersWithoutBeanName() {
+		get()
+			.withUserConfiguration(org.springframework.boot.test.context.example.duplicate.first.EmptyConfig.class,
+					org.springframework.boot.test.context.example.duplicate.second.EmptyConfig.class)
+			.run((context) -> assertThat(context.getStartupFailure())
+				.isInstanceOf(BeanDefinitionOverrideException.class));
+	}
+
+	@Test
+	void runFullyQualifiedNameConfigurationsRegistersFullyQualifiedBeanName() {
+		get().withConfiguration(FullyQualifiedNameConfigurations.of(FooConfig.class))
+			.run((context) -> assertThat(context).hasBean(FooConfig.class.getName()));
+	}
+
+	@Test
+	void runWithFullyQualifiedNameConfigurationsWhenHasSameShortClassNamedRegistersWithFullyQualifiedBeanName() {
+		get()
+			.withConfiguration(FullyQualifiedNameConfigurations.of(
+					org.springframework.boot.test.context.example.duplicate.first.EmptyConfig.class,
+					org.springframework.boot.test.context.example.duplicate.second.EmptyConfig.class))
+			.run((context) -> assertThat(context)
+				.hasSingleBean(org.springframework.boot.test.context.example.duplicate.first.EmptyConfig.class)
+				.hasSingleBean(org.springframework.boot.test.context.example.duplicate.second.EmptyConfig.class));
+	}
+
 	@Test
 	void runWithUserNamedBeanShouldRegisterBean() {
 		get().withBean("foo", String.class, () -> "foo").run((context) -> assertThat(context).hasBean("foo"));
@@ -384,4 +421,21 @@ abstract class AbstractApplicationContextRunnerTests<T extends AbstractApplicati
 
 	}
 
+	static class FullyQualifiedNameConfigurations extends Configurations {
+
+		protected FullyQualifiedNameConfigurations(Collection<Class<?>> classes) {
+			super(null, classes, Class::getName);
+		}
+
+		@Override
+		protected Configurations merge(Set<Class<?>> mergedClasses) {
+			return new FullyQualifiedNameConfigurations(mergedClasses);
+		}
+
+		static FullyQualifiedNameConfigurations of(Class<?>... classes) {
+			return new FullyQualifiedNameConfigurations(List.of(classes));
+		}
+
+	}
+
 }