Change getEnvironment() to return null by default

Update the `SpringBootContextLoader.getEnvironment()` method so that it
returns `null` rather than a new `StandardEnvironment`.

Closes gh-29405

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootContextLoader.java

@@ -42,7 +42,6 @@ import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.core.annotation.MergedAnnotations.SearchStrategy;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.env.ConfigurableEnvironment;
-import org.springframework.core.env.StandardEnvironment;
 import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.test.context.ContextConfigurationAttributes;
@@ -55,7 +54,6 @@ import org.springframework.test.context.support.TestPropertySourceUtils;
 import org.springframework.test.context.web.WebMergedContextConfiguration;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
-import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.context.support.GenericWebApplicationContext;
 
@@ -114,10 +112,8 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 			application.setWebApplicationType(WebApplicationType.NONE);
 		}
 		application.setInitializers(initializers);
-		boolean customEnvironent = ReflectionUtils.findMethod(getClass(), "getEnvironment")
-				.getDeclaringClass() != SpringBootContextLoader.class;
-		if (customEnvironent) {
-			ConfigurableEnvironment environment = getEnvironment();
+		ConfigurableEnvironment environment = getEnvironment();
+		if (environment != null) {
 			prepareEnvironment(config, application, environment, false);
 			application.setEnvironment(environment);
 		}
@@ -163,12 +159,13 @@ public class SpringBootContextLoader extends AbstractContextLoader {
 	}
 
 	/**
-	 * Builds a new {@link ConfigurableEnvironment} instance. You can override this method
-	 * to return something other than {@link StandardEnvironment} if necessary.
+	 * Returns the {@link ConfigurableEnvironment} instance that should be applied to
+	 * {@link SpringApplication} or {@code null} to use the default. You can override this
+	 * method if you need a custom environment.
 	 * @return a {@link ConfigurableEnvironment} instance
 	 */
 	protected ConfigurableEnvironment getEnvironment() {
-		return new StandardEnvironment();
+		return null;
 	}
 
 	protected String[] getInlinedProperties(MergedContextConfiguration config) {

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestWithActiveProfilesAndEnvironmentPropertyTests.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.
@@ -27,6 +27,7 @@ import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
 import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.env.MutablePropertySources;
+import org.springframework.core.env.StandardEnvironment;
 import org.springframework.test.context.ActiveProfiles;
 import org.springframework.test.context.ContextConfiguration;
 
@@ -61,7 +62,7 @@ class SpringBootTestWithActiveProfilesAndEnvironmentPropertyTests {
 
 		@Override
 		protected ConfigurableEnvironment getEnvironment() {
-			ConfigurableEnvironment environment = super.getEnvironment();
+			ConfigurableEnvironment environment = new StandardEnvironment();
 			MutablePropertySources sources = environment.getPropertySources();
 			Map<String, Object> map = new LinkedHashMap<>();
 			map.put("spring.profiles.active", "local");

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestWithActiveProfilesAndSystemEnvironmentPropertyTests.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.
@@ -64,7 +64,7 @@ class SpringBootTestWithActiveProfilesAndSystemEnvironmentPropertyTests {
 		@Override
 		@SuppressWarnings("unchecked")
 		protected ConfigurableEnvironment getEnvironment() {
-			ConfigurableEnvironment environment = super.getEnvironment();
+			ConfigurableEnvironment environment = new StandardEnvironment();
 			MutablePropertySources sources = environment.getPropertySources();
 			PropertySource<?> source = sources.get(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME);
 			Map<String, Object> map = new LinkedHashMap<>((Map<String, Object>) source.getSource());