### Question:
OptionGroup implements Serializable { public Collection<String> getNames() { return optionMap.keySet(); }  OptionGroup addOption(Option option); Collection<String> getNames(); Collection<Option> getOptions(); void setSelected(Option option); String getSelected(); void setRequired(boolean required); boolean isRequired(); @Override String toString();  }### Answer:
@Test public void testGetNames() { OptionGroup group = new OptionGroup(); group.addOption(OptionBuilder.create('a')); group.addOption(OptionBuilder.create('b')); assertNotNull("null names", group.getNames()); assertEquals(2, group.getNames().size()); assertTrue(group.getNames().contains("a")); assertTrue(group.getNames().contains("b")); }