DefaultDataFunctionRegistry implements DataFunctionRegistry { @Override public Set<String> getFunctions() { return functions.keySet(); } DefaultDataFunctionRegistry();  DefaultDataFunctionRegistry(boolean registerDefaults); @Override void register(String name, DataFunction<?> function); @Override DataFunction<?> getFunction(String name); @Override Set<String> getFunctions();  }
@Test public void testDefaultFunctions() { final DefaultDataFunctionRegistry registry = new DefaultDataFunctionRegistry(); final Set<String> functions = registry.getFunctions(); final Set<String> expected = new HashSet<>(Arrays.asList("count", "delete")); assertThat(functions, hasSize(2)); for (String function : functions) { assertThat(function, isIn(expected)); expected.remove(function); } assertThat(expected, is(Matchers.empty())); }