如何从单元测试中消除对数据库的依赖

Question

是否可以为此方法创建单元测试？

public void CheckIndicatorMeasurementRecordingValidity(IndicatorMeasurementRecording indicatorMeasurementRecording)
{
   var isDateRangeOverLapping = this.db.IndicatorMeasurementRecordingRepository.Any(r => r.IndicatorId == indicatorMeasurementRecording.Indicator.Id && r.Id != indicatorMeasurementRecording.Id
                && r.RecordingDateRange.ToDateTime >= indicatorMeasurementRecording.RecordingDateRange.FromDateTime
                && r.RecordingDateRange.FromDateTime <= indicatorMeasurementRecording.RecordingDateRange.ToDateTime);

   if (isDateRangeOverLapping)
   {
       throw new GrcUserException(IndicatorThresholdValidityManagementLocal.DateRangeOverlapping);
   }
}

我试过这样创建测试

[TestMethod]
public void Indicator_measurement_date_range_overlapping_shall_throw_exception()
{
    var indicator = new Indicator();
    var oldIndicatorMeasurementRecording = new IndicatorMeasurementRecording();
    var newIndicatorMeasurementRecording = new IndicatorMeasurementRecording();
    var errorMessage = string.Empty;

    oldIndicatorMeasurementRecording.Id = 1;
    oldIndicatorMeasurementRecording.RecordingDateRange.FromDateTime = DateTime.Today.AddDays(-5);
    oldIndicatorMeasurementRecording.RecordingDateRange.ToDateTime = DateTime.Today;
    indicator.IndicatorMeasurementRecordings.Add(oldIndicatorMeasurementRecording);

    oldIndicatorMeasurementRecording.Id = 2;
    newIndicatorMeasurementRecording.RecordingDateRange.FromDateTime = DateTime.Today.AddDays(-2);
    newIndicatorMeasurementRecording.RecordingDateRange.ToDateTime = DateTime.Today;
    newIndicatorMeasurementRecording.Indicator = indicator;

    try
    {
        this.indicatorValidityProxy.CheckIndicatorMeasurementRecordingValidity(newIndicatorMeasurementRecording);
    }
    catch (Exception ex)
    {
        errorMessage = ex.Message;
    }

    Assert.AreEqual(IndicatorThresholdValidityManagementLocal.DateRangeOverlapping, errorMessage);
}

问题是，测试总是失败，因为 this.db.IndicatorMeasurementRecordingRepository.Count 测试始终为 0。出于开发目的，它总是 returns 正确的数字。只有在测试的时候是0.

谁能告诉我为什么 this.db.IndicatorMeasurementRecordingRepository.Count 用于测试目的总是 0？为我的案例编写测试的最佳实践是什么？

Answer 1

我不确定 the.db 是什么，但假设 public class MyContext : DbContext 和 this.db 是 MyContext 类型，那么使用 Mock 你可以：

var contextMock = new Mock<MyContext>();
// arrange more

本质上，当 IndicatorMeasurementRecordingRepository 被查询时，您会将 contextMock 配置为 return 一组已知的对象（IndicatorMeasurementRecording？）。类似于：

var dbSetMock = new Mock<IDbSet<DbEntity>>();
dbSetMock.Setup(m => m.Provider).Returns(data.Provider);
dbSetMock.Setup(m => m.Expression).Returns(data.Expression);
dbSetMock.Setup(m => m.ElementType).Returns(data.ElementType);
dbSetMock.Setup(m => m.GetEnumerator()).Returns(data.GetEnumerator());

var contextMock = new Mock<MyContext>();
contextMock 
    .Setup(x => x.DbEntities)
    .Returns(dbSetMock.Object);

其中数据是要从模拟中return编辑的对象列表。

一些可以帮助您的链接/示例：

Moq quickstart is here.
Testing with a Mocking Framework（MSDN）
How to mock dbcontext and dbset with MOQ for Unit Testing（以上航空代码抄自此处）
How ef6 enables mocking dbsets more easily

我无法重新创建你的测试用例，因为那里没有太多代码，但如果你提供 mcve 我非常乐意更详细地查看测试。

如何从单元测试中消除对数据库的依赖

How to eliminate the dependency on the database from a unit test

c#

tdd

unit-testing