public function byDefaultHeadersOfTheSameNameAreReplaced()
{
$message = $this->getAbstractMessageMock();
$message->setHeader('MyHeader', 'MyValue');
$message->setHeader('MyHeader', 'OtherValue');
$expectedHeaders = ['MyHeader' => ['OtherValue']];
$this->assertEquals($expectedHeaders, $message->getHeaders()->getAll());
}