add test to verify reading of YAML tags

make sure it is able to read specs written with traits/mixins as
discussed in
https://github.com/OAI/OpenAPI-Specification/issues/613#issuecomment-203673611

Author: cebe

tests/ReaderTest.php

@@ -36,6 +36,47 @@ public function testReadYaml()
         $this->assertApiContent($openapi);
     }
 
+    /**
+     * Test if reading YAML file with anchors works
+     */
+    public function testReadYamlWithAnchors()
+    {
+        $openApiFile = __DIR__ . '/spec/data/traits-mixins.yaml';
+        $openapi = \cebe\openapi\Reader::readFromYamlFile($openApiFile);
+
+        $this->assertApiContent($openapi);
+
+        $putOperation = $openapi->paths['/foo']->put;
+        $this->assertEquals('create foo', $putOperation->description);
+        $this->assertTrue($putOperation->responses->hasResponse('200'));
+        $this->assertTrue($putOperation->responses->hasResponse('404'));
+        $this->assertTrue($putOperation->responses->hasResponse('428'));
+        $this->assertTrue($putOperation->responses->hasResponse('default'));
+
+        $respOk = $putOperation->responses->getResponse('200');
+        $this->assertEquals('request succeeded', $respOk->description);
+        $this->assertEquals('the request id', $respOk->headers['X-Request-Id']->description);
+
+        $resp404 = $putOperation->responses->getResponse('404');
+        $this->assertEquals('resource not found', $resp404->description);
+        $this->assertEquals('the request id', $resp404->headers['X-Request-Id']->description);
+
+        $resp428 = $putOperation->responses->getResponse('428');
+        $this->assertEquals('resource not found', $resp428->description);
+        $this->assertEquals('the request id', $resp428->headers['X-Request-Id']->description);
+
+        $respDefault = $putOperation->responses->getResponse('default');
+        $this->assertEquals('resource not found', $respDefault->description);
+        $this->assertEquals('the request id', $respDefault->headers['X-Request-Id']->description);
+
+        $foo = $openapi->components->schemas['Foo'];
+        $this->assertArrayHasKey('uuid', $foo->properties);
+        $this->assertArrayHasKey('name', $foo->properties);
+        $this->assertArrayHasKey('id', $foo->properties);
+        $this->assertArrayHasKey('description', $foo->properties);
+        $this->assertEquals('uuid of the resource', $foo->properties['uuid']->description);
+    }
+
     private function assertApiContent(\cebe\openapi\spec\OpenApi $openapi)
     {
         $result = $openapi->validate();

tests/spec/data/traits-mixins.yaml

@@ -0,0 +1,60 @@
+# test whether we can read YAML files that use mixin feature
+x-ResourceCommon: &ResourceCommon
+    uuid:
+      type: string
+      description: uuid of the resource
+    name:
+      type: string
+      description: name of the resource
+
+openapi: 3.0.0
+info:
+  title: Test API
+  version: 1.0.0
+paths:
+  /foo:
+    put:
+      description: create foo
+      responses:
+        '200': &RESP_OK
+          description: request succeeded
+          headers: &RESP_HEADERS
+            X-Request-Id:
+              description: the request id
+          schema:
+            $ref: '#/components/schemas/Foo'
+        '404': &RESP_ERROR
+          description: resource not found
+          headers: *RESP_HEADERS
+          schema:
+            $ref: "#/components/schemas/Error"
+        '428': *RESP_ERROR
+        default: *RESP_ERROR
+components:
+  responses:
+    Bar:
+      description: A bar
+      content:
+        application/json:
+          schema: { type: object }
+  schemas:
+    Error:
+      description: This is an error
+      type: object
+      properties:
+        message:
+          type: string
+        code:
+          type: number
+          format: int64
+    Foo:
+      description: A foo resource type
+      type: object
+      properties:
+        <<: *ResourceCommon
+        id:
+          type: string
+          description: id of the foo
+        description:
+          type: string
+          description: description of foo