@Override
			public void modifyPrivate(MergeProgram mergeProgram) throws Exception {
				Library library =
					mergeProgram.createExternalLibrary(libname, SourceType.USER_DEFINED);
				mergeProgram.createNamespace(library, label, SourceType.USER_DEFINED);

				Program program = mergeProgram.getProgram();
				ExternalManager externalManager = program.getExternalManager();
				assertTrue(externalManager.contains(libname));

				Symbol namespaceSymbol = getUniqueSymbol(program, label, library);
				assertNotNull(namespaceSymbol);
				assertEquals(SymbolType.NAMESPACE, namespaceSymbol.getSymbolType());

				assertTrue(namespaceSymbol.getSource() == SourceType.USER_DEFINED);
			}
Test the merge of the versioned program's listing.
Ghidra/Features/Base/src/test.slow/java/ghidra/app/merge/listing/ExternalMergerAddTest.java