public async Task TestUpdateAsync_VerifySaveChangesCalledOnce()
{
var contextOptions = new DbContextOptions <TaskManagerDbContext>();
var mockContext = new Mock <TaskManagerDbContext>(contextOptions);
var taskRepository = new TaskManagerRepository(mockContext.Object);
var taskDetail = new TaskItem()
{
Id = 1, Name = "Task 1 ", Priority = 10
};
var mockSet = new Mock <DbSet <TaskItem> >();
mockContext.Setup(m => m.Tasks).Returns(mockSet.Object);
await taskRepository.UpdateAsync(1, taskDetail);
mockSet.Verify(m => m.Update(taskDetail), Times.Once);
mockContext.Verify(m => m.SaveChangesAsync(System.Threading.CancellationToken.None), Times.Once);
}