SparkPost\Test\SparkPostTest::testGetHttpHeaders PHP Method

    public function testGetHttpHeaders()
    {
        $headers = $this->resource->getHttpHeaders(['Custom-Header' => 'testing']);
        $version = NSA::getProperty($this->resource, 'version');
        $this->assertEquals('SPARKPOST_API_KEY', $headers['Authorization']);
        $this->assertEquals('application/json', $headers['Content-Type']);
        $this->assertEquals('testing', $headers['Custom-Header']);
        $this->assertEquals('php-sparkpost/' . $version, $headers['User-Agent']);
    }