public void AllowSettingAssigneeToNull()
{
var issue = new Issue(new Project(new ApplicationUser(), "project"), "name", "description");
issue.Assignee.Should().Be(null);
issue.AssignUser(new ApplicationUser());
issue.Assignee.Should().NotBe(null);
issue.AssignUser(null);
issue.Assignee.Should().Be(null);
}