### Question:
FocusModeSelectors { public static SelectorFunction<Collection<FocusMode>, FocusMode> continuousFocus() { return focusMode(FocusMode.CONTINUOUS_FOCUS); }  static SelectorFunction<Collection<FocusMode>, FocusMode> fixed(); static SelectorFunction<Collection<FocusMode>, FocusMode> infinity(); static SelectorFunction<Collection<FocusMode>, FocusMode> macro(); static SelectorFunction<Collection<FocusMode>, FocusMode> autoFocus(); static SelectorFunction<Collection<FocusMode>, FocusMode> continuousFocus(); static SelectorFunction<Collection<FocusMode>, FocusMode> edof();  }### Answer:
@Test public void focusMode_Available() throws Exception { Set<FocusMode> availableModes = asSet( FocusMode.AUTO, FocusMode.CONTINUOUS_FOCUS, FocusMode.FIXED ); FocusMode result = FocusModeSelectors .continuousFocus() .select(availableModes); assertEquals( FocusMode.CONTINUOUS_FOCUS, result ); }
@Test public void focusMode_NotAvailable() throws Exception { Set<FocusMode> availableModes = asSet( FocusMode.AUTO, FocusMode.FIXED ); FocusMode result = FocusModeSelectors .continuousFocus() .select(availableModes); assertNull(result); }