public void TryToAcceptAlreadyAcceptedInvitation_GetException()
{
//Arrange
var testUser = new User("Petr", new Credentials("SomeEmail", "SomePassword"), true, UserType.User);
var invitation = new Invitation(IntIterator.GetNextId(), testUser.Id, IntIterator.GetNextId(),
MemberRole.Member, InvitationStatus.InProgress);
testUser.AddInvitation(invitation);
testUser.AcceptInvitation(invitation.Id);
//Act
testUser.AcceptInvitation(invitation.Id);
}