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

samples/junit5/src/docs/asciidoc/index.adoc

@@ -0,0 +1,22 @@
+= Spring REST Docs TestNG Sample
+Andy Wilkinson;
+:doctype: book
+:icons: font
+:source-highlighter: highlightjs
+
+Sample application demonstrating how to use Spring REST Docs with TestNG.
+
+`SampleTestNgApplicationTests` makes a call to a very simple service and produces three
+documentation snippets.
+
+One showing how to make a request using cURL:
+
+include::{snippets}/sample/curl-request.adoc[]
+
+One showing the HTTP request:
+
+include::{snippets}/sample/http-request.adoc[]
+
+And one showing the HTTP response:
+
+include::{snippets}/sample/http-response.adoc[]

samples/junit5/src/main/java/com/example/junit5/SampleJUnit5Application.java

@@ -0,0 +1,41 @@
+/*
+ * 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.junit5;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@SpringBootApplication
+public class SampleJUnit5Application {
+
+	public static void main(String[] args) {
+		new SpringApplication(SampleJUnit5Application.class).run(args);
+	}
+
+	@RestController
+	private static class SampleController {
+
+		@RequestMapping("/")
+		public String index() {
+			return "Hello, World";
+		}
+
+	}
+
+}

samples/junit5/src/test/java/com/example/junit5/SampleJUnit5ApplicationTests.java

@@ -0,0 +1,57 @@
+/*
+ * 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.junit5;
+
+import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
+import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.documentationConfiguration;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.restdocs.RestDocumentationExtension;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.context.WebApplicationContext;
+
+@SpringBootTest
+@ExtendWith({RestDocumentationExtension.class, SpringExtension.class})
+public class SampleJUnit5ApplicationTests {
+
+	@Autowired
+	private WebApplicationContext context;
+
+	private MockMvc mockMvc;
+
+	@BeforeEach
+	public void setUp(RestDocumentationExtension restDocumentation) {
+		this.mockMvc = MockMvcBuilders.webAppContextSetup(context)
+				.apply(documentationConfiguration(restDocumentation)).build();
+	}
+
+	@Test
+	public void sample() throws Exception {
+		this.mockMvc.perform(get("/"))
+				.andExpect(status().isOk())
+				.andDo(document("sample"));
+	}
+
+}