Introduce MockEnvironment in the spring-test module

For legacy reasons, a MockEnvironment implementation already exists in multiple places within Spring's test suite; however, it is not available to the general public.

This commit promotes MockEnvironment to a first-class citizen in the spring-test module, alongside the existing MockPropertySource.

In addition, the following house cleaning has been performed.

 - deleted MockPropertySource from the spring-expression module
 - deleted MockEnvironment from the "spring" integration testing module
 - updated test copies of MockPropertySource and MockEnvironment
 - documented MockEnvironment and MockPropertySource in the testing
   chapter of the reference manual

Issue: SPR-9492

spring-expression/src/test/java/org/springframework/mock/env/MockPropertySource.java

@@ -1,102 +0,0 @@
-/*
- * Copyright 2002-2011 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
- *
- *      http://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.mock.env;
-
-import java.util.Properties;
-
-import org.springframework.core.env.PropertiesPropertySource;
-import org.springframework.core.env.PropertySource;
-
-/**
- * Simple {@link PropertySource} implementation for use in testing. Accepts
- * a user-provided {@link Properties} object, or if omitted during construction,
- * the implementation will initialize its own.
- *
- * The {@link #setProperty} and {@link #withProperty} methods are exposed for
- * convenience, for example:
- * <pre>
- * {@code
- *   PropertySource<?> source = new MockPropertySource().withProperty("foo", "bar");
- * }
- * </pre>
- *
- * @author Chris Beams
- * @since 3.1
- */
-public class MockPropertySource extends PropertiesPropertySource {
-
-	/**
-	 * {@value} is the default name for {@link MockPropertySource} instances not
-	 * otherwise given an explicit name.
-	 * @see #MockPropertySource()
-	 * @see #MockPropertySource(String)
-	 */
-	public static final String MOCK_PROPERTIES_PROPERTY_SOURCE_NAME = "mockProperties";
-
-	/**
-	 * Create a new {@code MockPropertySource} named {@value #MOCK_PROPERTIES_PROPERTY_SOURCE_NAME}
-	 * that will maintain its own internal {@link Properties} instance.
-	 */
-	public MockPropertySource() {
-		this(new Properties());
-	}
-
-	/**
-	 * Create a new {@code MockPropertySource} with the given name that will
-	 * maintain its own internal {@link Properties} instance.
-	 * @param name the {@linkplain #getName() name} of the property source
-	 */
-	public MockPropertySource(String name) {
-		this(name, new Properties());
-	}
-
-	/**
-	 * Create a new {@code MockPropertySource} named {@value #MOCK_PROPERTIES_PROPERTY_SOURCE_NAME}
-	 * and backed by the given {@link Properties} object.
-	 * @param properties the properties to use
-	 */
-	public MockPropertySource(Properties properties) {
-		this(MOCK_PROPERTIES_PROPERTY_SOURCE_NAME, properties);
-	}
-
-	/**
-	 * Create a new {@code MockPropertySource} with with the given name and backed by the given
-	 * {@link Properties} object
-	 * @param name the {@linkplain #getName() name} of the property source
-	 * @param properties the properties to use
-	 */
-	public MockPropertySource(String name, Properties properties) {
-		super(name, properties);
-	}
-
-	/**
-	 * Set the given property on the underlying {@link Properties} object.
-	 */
-	public void setProperty(String name, Object value) {
-		this.source.put(name, value);
-	}
-
-	/**
-	 * Convenient synonym for {@link #setProperty} that returns the current instance.
-	 * Useful for method chaining and fluent-style use.
-	 * @return this {@link MockPropertySource} instance
-	 */
-	public MockPropertySource withProperty(String name, Object value) {
-		this.setProperty(name, value);
-		return this;
-	}
-}