mock http headers without clearing out content type headers

src/Mock/MockRequestMatcher.php

@@ -149,6 +149,18 @@ public function withHeaders(IHeaders $headers) : MockRequestMatcher {
         return $request;
     }
 
+    /**
+     * Return an instance with the specified HTTP headers added to existing mocked HTTP headers.
+     *
+     * @param IHeaders $headers
+     * @return MockRequestMatcher
+     */
+    public function withAddedHeaders(IHeaders $headers) : MockRequestMatcher {
+        $request = clone $this;
+        $request->headers->addHeaders($headers);
+        return $request;
+    }
+
     /**
      * Return an instance with the specified body string
      *

tests/Mock/MockRequestMatcher/withAddedHeaders_Test.php

@@ -0,0 +1,58 @@
+<?php declare(strict_types=1);
+/**
+ * MindTouch HTTP
+ * Copyright (C) 2006-2018 MindTouch, Inc.
+ * www.mindtouch.com  [email protected]
+ *
+ * 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.
+ */
+namespace MindTouch\Http\tests\Mock\MockRequestMatcher;
+
+use MindTouch\Http\Content\ContentType;
+use MindTouch\Http\Content\UrlEncodedFormDataContent;
+use MindTouch\Http\Headers;
+use MindTouch\Http\HttpPlug;
+use MindTouch\Http\Mock\MockRequestMatcher;
+use MindTouch\Http\tests\MindTouchHttpUnitTestCase;
+use MindTouch\Http\XUri;
+
+class withAddedHeaders_Test extends MindTouchHttpUnitTestCase  {
+
+    /**
+     * @test
+     */
+    public function Can_add_headers() {
+
+        // arrange
+        $matcher = (new MockRequestMatcher(HttpPlug::METHOD_POST, XUri::tryParse('http://example.com/bazz')))
+            ->withHeaders(Headers::newFromHeaderNameValuePairs([
+                ['X-Qux', 'foo']
+            ]))
+            ->withContent(new UrlEncodedFormDataContent([
+                'baz' => 'qux'
+            ]))
+            ->withAddedHeaders(Headers::newFromHeaderNameValuePairs([
+                ['X-Fred', 'plugh']
+            ]));
+
+        // act
+        $result = $matcher->getHeaders();
+
+        // assert
+        $this->assertEquals([
+            'X-Qux: foo',
+            'Content-Type: ' . ContentType::FORM_URLENCODED,
+            'X-Fred: plugh'
+        ], $result->toRawHeaders());
+    }
+}