public void FollowUser_UserIsAlreadyFollowing_ThrowAnInvalidOperationException()
{
_repository.Setup(repo => repo.Table).Returns(new List <Follow>
{
_follow
}.AsQueryable());
Assert.That(async() => await _followService.FollowUserAsync(_followeeId),
Throws.InvalidOperationException);
_repository.Verify(repo => repo.AddAsync(It.IsAny <Follow>()), Times.Never);
}