Improve unit testing of StandardTemplateResourceResolver

spring-restdocs-core/src/test/java/org/springframework/restdocs/templates/StandardTemplateResourceResolverTests.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2014-2015 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.restdocs.templates;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import java.net.URL;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Callable;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.springframework.core.io.Resource;
+
+/**
+ * Tests for {@link TemplateResourceResolver}.
+ * 
+ * @author Andy Wilkinson
+ */
+public class StandardTemplateResourceResolverTests {
+
+	@Rule
+	public final ExpectedException thrown = ExpectedException.none();
+
+	private final TemplateResourceResolver resolver = new StandardTemplateResourceResolver();
+
+	private final TestClassLoader classLoader = new TestClassLoader();
+
+	@Test
+	public void customSnippetResolution() throws Exception {
+		this.classLoader.addResource(
+				"org/springframework/restdocs/templates/test.snippet", getClass()
+						.getResource("test.snippet"));
+		Resource snippet = doWithThreadContextClassLoader(this.classLoader,
+				new Callable<Resource>() {
+
+					@Override
+					public Resource call() {
+						return StandardTemplateResourceResolverTests.this.resolver
+								.resolveTemplateResource("test");
+					}
+
+				});
+
+		assertThat(snippet.getURL(), is(equalTo(getClass().getResource("test.snippet"))));
+	}
+
+	@Test
+	public void fallsBackToDefaultSnippet() throws Exception {
+		this.classLoader.addResource(
+				"org/springframework/restdocs/templates/default-test.snippet", getClass()
+						.getResource("test.snippet"));
+		Resource snippet = doWithThreadContextClassLoader(this.classLoader,
+				new Callable<Resource>() {
+
+					@Override
+					public Resource call() {
+						return StandardTemplateResourceResolverTests.this.resolver
+								.resolveTemplateResource("test");
+					}
+
+				});
+
+		assertThat(snippet.getURL(), is(equalTo(getClass().getResource("test.snippet"))));
+	}
+
+	@Test
+	public void failsIfCustomAndDefaultSnippetDoNotExist() throws Exception {
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage(equalTo("Template named 'test' could not be resolved"));
+		doWithThreadContextClassLoader(this.classLoader, new Callable<Resource>() {
+
+			@Override
+			public Resource call() {
+				return StandardTemplateResourceResolverTests.this.resolver
+						.resolveTemplateResource("test");
+			}
+
+		});
+	}
+
+	private <T> T doWithThreadContextClassLoader(ClassLoader classLoader,
+			Callable<T> action) throws Exception {
+		ClassLoader previous = Thread.currentThread().getContextClassLoader();
+		Thread.currentThread().setContextClassLoader(classLoader);
+		try {
+			return action.call();
+		}
+		finally {
+			Thread.currentThread().setContextClassLoader(previous);
+		}
+	}
+
+	private static class TestClassLoader extends ClassLoader {
+
+		private Map<String, URL> resources = new HashMap<>();
+
+		private void addResource(String name, URL url) {
+			this.resources.put(name, url);
+		}
+
+		@Override
+		public URL getResource(String name) {
+			return this.resources.get(name);
+		}
+
+	}
+
+}