Add Referrer-Policy header support

Fixes gh-4110

web/src/test/java/org/springframework/security/web/header/writers/ReferrerPolicyHeaderWriterTests.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2002-2016 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 org.springframework.security.web.header.writers;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.security.web.header.writers.ReferrerPolicyHeaderWriter.*;
+
+/**
+ * @author Eddú Meléndez
+ */
+public class ReferrerPolicyHeaderWriterTests {
+
+	private final String DEFAULT_REFERRER_POLICY = "no-referrer";
+	private MockHttpServletRequest request;
+	private MockHttpServletResponse response;
+	private ReferrerPolicyHeaderWriter writer;
+
+	@Before
+	public void setup() {
+		this.request = new MockHttpServletRequest();
+		this.request.setSecure(true);
+		this.response = new MockHttpServletResponse();
+		this.writer = new ReferrerPolicyHeaderWriter();
+	}
+
+	@Test
+	public void writeHeadersReferrerPolicyDefault() {
+		this.writer.writeHeaders(this.request, this.response);
+
+		assertThat(this.response.getHeaderNames().size()).isEqualTo(1);
+		assertThat(this.response.getHeader("Referrer-Policy")).isEqualTo(DEFAULT_REFERRER_POLICY);
+	}
+
+	@Test
+	public void writeHeadersReferrerPolicyCustom() {
+		this.writer = new ReferrerPolicyHeaderWriter(ReferrerPolicy.SAME_ORIGIN);
+
+		this.writer.writeHeaders(this.request, this.response);
+
+		assertThat(this.response.getHeaderNames().size()).isEqualTo(1);
+		assertThat(this.response.getHeader("Referrer-Policy")).isEqualTo("same-origin");
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void writeHeaderReferrerPolicyInvalid() {
+		this.writer = new ReferrerPolicyHeaderWriter(null);
+	}
+
+}