public function testWithAddedHeader() { $param = 'header'; $param2 = 'value'; $this->responseMock->shouldReceive('withAddedHeader')->andReturn($this->returnValue); $sparkpostResponse = new SparkPostResponse($this->responseMock); $this->assertEquals($this->responseMock->withAddedHeader($param, $param2), $sparkpostResponse->withAddedHeader($param, $param2)); }