### Question:
HasDisplayTextWithArgs implements IHasDisplayText { @Nullable public String getDisplayText (@Nonnull final Locale aContentLocale) { final String sText = m_aParentText.getDisplayText (aContentLocale); return TextHelper.getFormattedText (sText, m_aArgs); } HasDisplayTextWithArgs(@Nonnull final IHasDisplayText aParentText, @Nonnull @Nonempty final Object... aArgs); @Nonnull IHasDisplayText getParentText(); @Nonnull @Nonempty @ReturnsMutableCopy Object [] getAllArgs(); @Nullable String getDisplayText(@Nonnull final Locale aContentLocale); @Override String toString();  }### Answer:
@Test public void testAll () { final IHasDisplayText t = new MockHasDisplayText (L_DE, "Hallo {0}"); final HasDisplayTextWithArgs x = new HasDisplayTextWithArgs (t, "Welt"); assertEquals ("Hallo Welt", x.getDisplayText (L_DE)); assertNull (x.getDisplayText (L_FR)); CommonsTestHelper.testToStringImplementation (x); try { new HasDisplayTextWithArgs (null, "abc"); fail (); } catch (final NullPointerException ex) {} try { new HasDisplayTextWithArgs (new MockHasDisplayText (L_DE, "de")); fail (); } catch (final IllegalArgumentException ex) {} }