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