code: public void expectErrorsForTag(String tag) {
      checkTag(tag);
      if (UNPREVENTABLE_TAGS.contains(tag)) {
        throw new AssertionError("Tag `" + tag + "` is already suppressed.");
      }
      expectedTags.add(tag);
    }
docs: Blanket suppress test failures due to errors from a tag. If this tag is not printed at
  Log.ERROR during test execution, the test case will fail (unless {@link
  #ignoreMissingLoggedTags()} is used).
  
  <p>Avoid using this method when possible. Prefer to assert on the presence of a specific
  message using {@link #expectLogMessage} in test cases that *intentionally* trigger an error.