public function signMustChangeTheSignature()
{
$signer = $this->createMock(Signer::class);
$signature = $this->createMock(Signature::class);
$signer->expects($this->any())->method('sign')->willReturn($signature);
$builder = $this->createBuilder();
$builder->sign($signer, new Key('test'));
self::assertAttributeSame($signature, 'signature', $builder);
}