public async Task GetAssignmentByIdAsync_ReturnsAssignment_WhenAssignmentExists()
{
// Arrange
var assignmentId = Guid.NewGuid();
var assignmentDto = new AssignmentDto {
Id = assignmentId, Name = "Assignment"
};
_stubAssignmentService.Setup(x => x.GetAssignmentByIdAsync(assignmentId))
.ReturnsAsync(assignmentDto);
// Act
var actionResult = await _assignmentsController.GetAssignmentByIdAsync(assignmentId);
var result = actionResult.Result as OkObjectResult;
var assignment = result.Value as AssignmentDto;
// Assert
Assert.AreEqual(assignmentId, assignment.Id);
}