### Question:
DDocFacade implements Serializable { public List<Signature> getSignatures() { List<Signature> signatures = new ArrayList<>(); ArrayList dDocSignatures = ddoc.getSignatures(); if (dDocSignatures == null) { return signatures; } int signatureIndexInArray = 0; for (Object signature : dDocSignatures) { DDocSignature finalSignature = mapDDoc4JSignatureToDigiDoc4J((org.digidoc4j.ddoc.Signature) signature); if (finalSignature != null) { finalSignature.setIndexInArray(signatureIndexInArray); signatures.add(finalSignature); signatureIndexInArray++; } } return signatures; } DDocFacade(Configuration configuration);   DDocFacade(SignedDoc ddoc); String getSignatureProfile(); DigestAlgorithm getDigestAlgorithm(); List<DataFile> getDataFiles(); int countDataFiles(); void save(String path); void save(OutputStream out); List<Signature> getSignatures(); Signature getSignature(int index); int countSignatures(); Container.DocumentType getDocumentType(); ContainerValidationResult validate(); String getVersion(); String getFormat(); Configuration getConfiguration();  }### Answer:
@Test public void getSignatureByIndex() { DDocFacade facade = openDDocFacade("src/test/resources/testFiles/valid-containers/ddoc_for_testing.ddoc"); Assert.assertEquals("497c5a2bfa9361a8534fbed9f48e7a12", facade.getSignatures().get(0).getSigningCertificate().getSerial()); }
@Test public void getSignatureWhenNotSigned() { DDocFacade facade = openDDocFacade("src/test/resources/testFiles/invalid-containers/signature_without_last_certificate.ddoc"); Assert.assertTrue(facade.getSignatures().isEmpty()); }