public void addAndRemove() throws Exception {
final Collaborators collaborators = this.collaborators();
final String login = "some_user";
collaborators.add(login);
MatcherAssert.assertThat(
collaborators.iterate(),
Matchers.<User>iterableWithSize(1)
);
MatcherAssert.assertThat(
collaborators.iterate().iterator().next().login(),
Matchers.equalTo(login)