Fix MockHttpServletRequest.setCookies to produce single cookie header

Prior to this commit, MockHttpServletRequest.setCookies() produced one
Cookie header per supplied cookie, resulting in multiple Cookie headers
which violates the specification.

This commit fixes this by ensuring that all cookie name-value pairs are
stored under a single Cookie header, separated by a semicolon.

Closes gh-23074

Author: L00kian

spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -41,6 +41,7 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.TimeZone;
+import java.util.stream.Collectors;
 import javax.servlet.AsyncContext;
 import javax.servlet.DispatcherType;
 import javax.servlet.RequestDispatcher;
@@ -58,6 +59,7 @@
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
+import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedCaseInsensitiveMap;
@@ -951,14 +953,20 @@ public String getAuthType() {
 
 	public void setCookies(@Nullable Cookie... cookies) {
 		this.cookies = (ObjectUtils.isEmpty(cookies) ? null : cookies);
-		this.headers.remove(HttpHeaders.COOKIE);
-		if (this.cookies != null) {
-			Arrays.stream(this.cookies)
-					.map(c -> c.getName() + '=' + (c.getValue() == null ? "" : c.getValue()))
-					.forEach(value -> doAddHeaderValue(HttpHeaders.COOKIE, value, false));
+		if (this.cookies == null) {
+			removeHeader(HttpHeaders.COOKIE);
+		}
+		else {
+			doAddHeaderValue(HttpHeaders.COOKIE, encodeCookies(this.cookies), true);
 		}
 	}
 
+	private static String encodeCookies(@NonNull Cookie... cookies) {
+		return Arrays.stream(cookies)
+				.map(c -> c.getName() + '=' + (c.getValue() == null ? "" : c.getValue()))
+				.collect(Collectors.joining("; "));
+	}
+
 	@Override
 	@Nullable
 	public Cookie[] getCookies() {
@@ -1272,6 +1280,7 @@ public HttpSession getSession() {
 	 * Otherwise it simply returns the current session id.
 	 * @since 4.0.3
 	 */
+	@Override
 	public String changeSessionId() {
 		Assert.isTrue(this.session != null, "The request does not have a session");
 		if (this.session instanceof MockHttpSession) {

spring-test/src/test/java/org/springframework/mock/web/MockHttpServletRequestTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -259,7 +259,9 @@ public void cookies() {
 		assertEquals("bar", cookies[0].getValue());
 		assertEquals("baz", cookies[1].getName());
 		assertEquals("qux", cookies[1].getValue());
-		assertEquals(Arrays.asList("foo=bar", "baz=qux"), cookieHeaders);
+
+		assertEquals(1, cookieHeaders.size());
+		assertEquals("foo=bar; baz=qux", cookieHeaders.get(0));
 	}
 
 	@Test