anchor.diff:  <% if repository.arez? -%>
       org.realityforge.braincheck.BrainCheckTestUtil.resetConfig( false );
       arez.ArezTestUtil.resetConfig( false );
  +    setIgnoreObserverErrors( false );
  +    setPrintObserverErrors( true );
  +    _observerErrors.clear();
  +    arez.Arez.context().addObserverErrorHandler( this::onObserverError );
   <% end -%>
       super.preTest();
   <% repository.gwt.test_factories.each do |short_code, classname| -%>
  
positive.code:   implements org.testng.IHookable
  <% end -%>
  {
  <% repository.gwt.test_factories.each do |short_code, classname| -%>
    @javax.annotation.Nonnull
    @edu.umd.cs.findbugs.annotations.SuppressFBWarnings( "NP_NONNULL_FIELD_NOT_INITIALIZED_IN_CONSTRUCTOR" )
  
negative.code:     super.postTest();
      arez.ArezTestUtil.resetConfig( true );
      org.realityforge.braincheck.BrainCheckTestUtil.resetConfig( true );
  <% if repository.arez? -%>
      if ( !_ignoreObserverErrors && !_observerErrors.isEmpty() )
      {
        org.testng.Assert.fail( "Unexpected Observer Errors: " + _observerErrors.stream().collect( java.util.stream.Collectors.joining( "\n" ) ) );
      }
  <% end -%>
    }
  
    @Override
  