### Question:
Context { public Set<String> getKeys() { return Collections.unmodifiableSet(values.keySet()); }  Set<String> getKeys(); String get(String key); void put(String key, String value); Map<String, Context> getChildren(); Context getChild(String name); Context createChild(String name); void remove(String nameOrKey); void setId(String id); String getId(); @Override String toString();  }### Answer:
@Test public void testEmptyContext_shouldHaveNoKeys() throws Exception { assertThat(context.getKeys().size(), is(0)); }
@Test(expected = UnsupportedOperationException.class) public void testIfGetKeysValuesAreUnmodifiable_shouldBeUnmodifiable() throws Exception { context.getKeys().clear(); }