### Question:
OverridableReadOnlyPropertiesImpl implements OverridableReadOnlyProperties { @Override public String getRequiredProperty(String key) { String value = getProperty(key); if (value == null) { throw new IllegalStateException(key + " property is required!"); } return value; } OverridableReadOnlyPropertiesImpl(Properties... propertieses);  OverridableReadOnlyPropertiesImpl(List<Properties> propertieses); @Override String getProperty(String key); @Override String getProperty(String key, String defaultValue); @Override String getRequiredProperty(String key);  }### Answer:
@Test public void getRequiredProperty_no_value() throws Exception { expectedException.expect(IllegalStateException.class); overridableReadOnlyPropertiesImpl.getRequiredProperty("some.not.exists.key"); }