public function testGetAllHeadersReturnsArrayOfStoredHeaders()
{
$msg = $this->getMockForAbstractClass('Amp\\Artax\\Message');
$msg->setHeader('My-Header1', 'val');
$msg->setHeader('My-Header2', ['val1', 'val2']);
$expected = ['My-Header1' => ['val'], 'My-Header2' => ['val1', 'val2']];
$this->assertEquals($expected, $msg->getAllHeaders());
}