SparkPost\Test\SparkPostTest::testSuccessfulAsyncRequestWithThen PHP Method

    public function testSuccessfulAsyncRequestWithThen()
    {
        $responseBody = ['results' => 'yay'];
        $responseMock = Mockery::mock('Psr\\Http\\Message\\ResponseInterface');
        $responseBodyMock = Mockery::mock();
        $responseMock->shouldReceive('getStatusCode')->andReturn(200);
        $responseMock->shouldReceive('getBody')->andReturn($responseBodyMock);
        $responseBodyMock->shouldReceive('__toString')->andReturn(json_encode($responseBody));
        $guzzlePromise = new GuzzleFulfilledPromise($responseMock);
        $promise = new SparkPostPromise(new GuzzleAdapterPromise($guzzlePromise, $this->resource->buildRequest('POST', 'transmissions', $this->postTransmissionPayload, [])));
        $promise->then(function ($exception) use($responseBody) {
            $this->assertEquals(200, $exception->getStatusCode());
            $this->assertEquals($responseBody, $exception->getBody());
        }, null)->wait();
    }