Add support for JUnit 5

This commit adds support for JUnit 5 and its Jupiter programming
model. A new Jupiter Extension implementation,
RestDocumentationExtension, is provided. This extension can be applied
to a test class to allow it to use Spring REST Docs to document a
RESTful API.

Closes gh-296

docs/src/test/java/com/example/mockmvc/ExampleApplicationJUnit5Tests.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2014-2016 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 com.example.mockmvc;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.restdocs.RestDocumentationContextProvider;
+import org.springframework.restdocs.RestDocumentationExtension;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.context.WebApplicationContext;
+
+import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.documentationConfiguration;
+
+@ExtendWith(RestDocumentationExtension.class)
+public class ExampleApplicationJUnit5Tests {
+
+	@SuppressWarnings("unused")
+	// tag::setup[]
+	private MockMvc mockMvc;
+
+	@BeforeEach
+	public void setUp(WebApplicationContext webApplicationContext,
+			RestDocumentationContextProvider restDocumentation) {
+		this.mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext)
+				.apply(documentationConfiguration(restDocumentation)) // <1>
+				.build();
+	}
+	// end::setup[]
+
+}

docs/src/test/java/com/example/restassured/ExampleApplicationJUnit5Tests.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2014-2017 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 com.example.restassured;
+
+import io.restassured.builder.RequestSpecBuilder;
+import io.restassured.specification.RequestSpecification;
+import org.junit.Before;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.restdocs.RestDocumentationContextProvider;
+import org.springframework.restdocs.RestDocumentationExtension;
+
+import static org.springframework.restdocs.restassured3.RestAssuredRestDocumentation.documentationConfiguration;
+
+@ExtendWith(RestDocumentationExtension.class)
+public class ExampleApplicationJUnit5Tests {
+
+	@SuppressWarnings("unused")
+	// tag::setup[]
+	private RequestSpecification spec;
+
+	@Before
+	public void setUp(RestDocumentationContextProvider restDocumentation) {
+		this.spec = new RequestSpecBuilder()
+				.addFilter(documentationConfiguration(restDocumentation)) // <1>
+				.build();
+	}
+	// end::setup[]
+}