Bug 239015 [Databinding] ObservableListTreeContentProvider adds the value passed to TreeViewer#setInput() to the known-elements
The input element is never shown in the viewer so it should no get part of the knownElements further more it restricts the usability of the content-provider because the input-element itself already has to provide the required Observable-Attribute(s).
tests/org.eclipse.jface.tests.databinding/src/org/eclipse/jface/tests/databinding/BindingTestSuite.java
public BindingTestSuite() {
		
		addTestSuite(AggregateValidationStatusTest.class);
		addTestSuite(DatabindingContextTest.class);
		addTestSuite(ListBindingTest.class);
		addTestSuite(UpdateStrategyTest.class);
		addTestSuite(UpdateValueStrategyTest.class);
		addTestSuite(ValueBindingTest.class);
		addTestSuite(ObservablesManagerTest.class);
		
		addTestSuite(BeansObservablesTest.class);
		addTestSuite(PojoObservablesTest.class);
		
		addTestSuite(NumberToStringConverterTest.class);
		addTestSuite(StringToNumberConverterTest.class);
		
		addTest(AbstractObservableTest.suite());
		addTestSuite(Diffs_ListDiffTests.class);
		addTestSuite(DiffsTest.class);
		addTestSuite(ObservablesTest.class);
		addTestSuite(ObservableTrackerTest.class);
		addTestSuite(RealmTest.class);
		
		addTest(AbstractObservableListTest.suite());
		addTest(ComputedListTest.suite());
		addTestSuite(ListDiffTest.class);
		addTestSuite(ListDiffVisitorTest.class);
		addTest(ObservableListTest.suite());
		addTest(WritableListTest.suite());