### Question:
Profill { public void addFillingProvider(FillingProvider provider) { throwIfInThreadSafeMode(); checkNotNull(provider); if (!matchers.containsValue(provider)) { PropertyMatcher matcher = createPropertyMatcher(provider); matchers.put(matcher, provider); } } Profill(); void makeSafeAgainstMultiThreadedAccess(); void addFillingProvider(FillingProvider provider); void fill(Object bean); boolean isTryToInstantiateIfNestedPropertyIsNull(); void setTryToInstantiateIfNestedPropertyIsNull(boolean value);  }### Answer:
@Test public void 同じクラスのFillingProviderを追加しても登録されるのは1つだけ() { profill.addFillingProvider(new AnnotatedStringLiteralFillingProvider()); profill.addFillingProvider(new AnnotatedStringLiteralFillingProvider()); assertThat(profill.matchers.size(), is(1)); }
@Test(expected = InternalException.class) public void FillingProviderにnullを指定できない() { profill.addFillingProvider(null); }