Add support for manually managing the RestDocumentationContext

In 1.0, the reliance on JUnit was more widespread than it should have
been. It should have been isolated to the JUnit TestRule implementation,
RestDocumentation. Unfortunately, RestDocumentation was also an argument
to MockMvcRestDocumentation.documentationConfiguration which made it
impossible to use Spring REST Docs without having JUnit on the
classpath.

This commit introduces JUnitRestDocumentation and
ManualRestDocumentation. The format is a direct replacement for
RestDocumentation which has been reworked to delegate to
JUnitRestDocumentation. The latter allows manual management of the
RestDocumentationContext, primarily for use with TestNG.

A new interface, RestDocumentationContextProvider, has been introduced.
It is implemented by RestDocumentation, JUnitRestDocumentation and
ManualRestDocumentation.
MockMvcRestDocumentation.documentationConfiguration has been overridden
to also accept a RestDocumentationContextProvider. The method that
accepts a RestDocumentation has been deprecated, as has
RestDocumentation itself.

The documentation has been updated to encourage the use of
JUnitRestDocumentation and a sample illustrating the use of Spring REST
Docs with TestNG has been added.

Closes gh-171

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

@@ -0,0 +1,21 @@
+= Spring REST Docs TestNG Sample
+Andy Wilkinson;
+:doctype: book
+:icons: font
+:source-highlighter: highlightjs
+
+This sample application demonstrates how to use Spring REST Docs with TestNG.
+`SampleTestNgApplication` 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/testng/src/main/java/com/example/testng/SampleTestNgApplication.java

@@ -0,0 +1,41 @@
+/*
+ * 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.testng;
+
+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 SampleTestNgApplication {
+
+	public static void main(String[] args) {
+		new SpringApplication(SampleTestNgApplication.class).run(args);
+	}
+
+	@RestController
+	private static class SampleController {
+
+		@RequestMapping("/")
+		public String index() {
+			return "Hello, World";
+		}
+
+	}
+
+}

samples/testng/src/test/java/com/example/testng/SampleTestNgApplicationTests.java

@@ -0,0 +1,68 @@
+/*
+ * 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.testng;
+
+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 java.lang.reflect.Method;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.restdocs.ManualRestDocumentation;
+import org.springframework.test.context.testng.AbstractTestNGSpringContextTests;
+import org.springframework.test.context.web.WebAppConfiguration;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.context.WebApplicationContext;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+@SpringApplicationConfiguration(classes=SampleTestNgApplication.class)
+@WebAppConfiguration
+public class SampleTestNgApplicationTests extends AbstractTestNGSpringContextTests {
+
+	private final ManualRestDocumentation restDocumentation = new ManualRestDocumentation("build/generated-snippets");
+
+	@Autowired
+	private WebApplicationContext context;
+
+	private MockMvc mockMvc;
+
+	@BeforeMethod
+	public void setUp(Method method) {
+		this.mockMvc = MockMvcBuilders.webAppContextSetup(context)
+				.apply(documentationConfiguration(this.restDocumentation)).build();
+		this.restDocumentation.beforeTest(getClass(), method.getName());
+	}
+
+	@AfterMethod
+	public void tearDown() {
+		this.restDocumentation.afterTest();
+	}
+
+	@Test
+	public void sample() throws Exception {
+		this.mockMvc.perform(get("/"))
+				.andExpect(status().isOk())
+				.andDo(document("sample"));
+	}
+
+}