@Test
void getOnlyElementWithEmptyCollection() {
PreconditionViolationException exception =
expectThrows(
PreconditionViolationException.class,
() -> {
CollectionUtils.getOnlyElement(emptySet());
});
assertEquals("collection must contain exactly one element: []", exception.getMessage());
}
@Test
void getOnlyElementWithMultiElementCollection() {
PreconditionViolationException exception =
expectThrows(
PreconditionViolationException.class,
() -> {
CollectionUtils.getOnlyElement(asList("foo", "bar"));
});
assertEquals("collection must contain exactly one element: [foo, bar]", exception.getMessage());
}
@Test
void getOnlyElementWithNullCollection() {
PreconditionViolationException exception =
expectThrows(
PreconditionViolationException.class,
() -> {
CollectionUtils.getOnlyElement(null);
});
assertEquals("collection must not be null", exception.getMessage());
}
