### Question:
OverrideSources { public static OverrideSource empty() { return OverridingSourceHolder.EMPTY; } private  OverrideSources(); static OverrideSource empty(); static OverrideSource create(Map<String, String> overrideValues); static ClasspathOverrideSource.Builder classpath(String resourceName); static FileOverrideSource.Builder file(String file); static UrlOverrideSource.Builder url(URL url);  }### Answer:
@Test public void testEmptyIsAlwaysTheSameInstance() { assertThat(OverrideSources.empty(), sameInstance(OverrideSources.empty())); }