@Test
  public void testExistingManifest() throws IOException, RegistryException {
    RegistryClient registryClient =
        RegistryClient.factory(EventHandlers.NONE, "gcr.io", "distroless/base", httpClient)
            .newRegistryClient();

    Optional<ManifestAndDigest<ManifestTemplate>> manifestDescriptor =
        registryClient.checkManifest(KNOWN_MANIFEST);

    assertTrue(manifestDescriptor.isPresent());
    assertEquals(KNOWN_MANIFEST, manifestDescriptor.get().getDigest().toString());
  }
A fictitious sha to test unknown images.
jib-core/src/integration-test/java/com/google/cloud/tools/jib/registry/ManifestCheckerIntegrationTest.java