### Question:
GlobalVariablesElement extends ElementDefinition<String> { static FeatureMap.Entry extensionOf(String variable) { return new EStructuralFeatureImpl.SimpleFeatureMapEntry( (EStructuralFeature.Internal) DOCUMENT_ROOT__GLOBAL, globalTypeDataOf(variable)); } GlobalVariablesElement(String name); @Override String getValue(BaseElement element); @Override void setValue(BaseElement element, String value);  }### Answer:
@Test public void testExtensionOf() { GlobalVariablesElement globalVariablesElement = new GlobalVariablesElement(NAME); GlobalType globalType = globalVariablesElement.globalTypeDataOf(GLOBAL_VARIABLE); FeatureMap.Entry entry = globalVariablesElement.extensionOf(GLOBAL_VARIABLE); assertNotNull(entry); assertTrue(entry instanceof EStructuralFeatureImpl.SimpleFeatureMapEntry); assertEquals(DOCUMENT_ROOT__GLOBAL, entry.getEStructuralFeature()); assertNotNull(entry.getValue()); assertEquals(globalType.getIdentifier(), ((GlobalType) entry.getValue()).getIdentifier()); assertEquals(globalType.getType(), ((GlobalType) entry.getValue()).getType()); }