private void checkCompletion() {
      Assert.assertEquals(1.0, lastProgress, DOUBLE_ERROR_MARGIN);
      Assert.assertTrue(areTasksFinished);
    }
Helper class to hold a {@link ProgressEventHandler} and verify that it handles a full progress.
jib-core/src/integration-test/java/com/google/cloud/tools/jib/api/ContainerizerIntegrationTest.java