模拟存储库返回 null

Question

我正在为服务编写一个简单的 xunit 测试用例 class。我嘲笑了 _userAPIRepository 但它 returns null 值。它应该 return teacherDetails.

下面是服务class方法和xunit测试用例方法。

服务方式

public async Task<List<TeacherDto>> GetTeacherDetails(Teacher teacher)
{
    List<TeacherDto> teacherDetails = new List<TeacherDto>();
    UserByUsername userByUsername = new UserByUsername
    {
        Username = teacher.Name,
        Id       = teacher.Id
    };

    teacherDetails = await _userServiceAPI.GetUserIdsByName(userByUsername);
         
    return teacherDetails;
         
}

xunit 测试用例

[Fact()]
public async Task GetUserDetails()
{
    //Arrange
    List<TeacherDto> teacherDetails = ServiceDataSource.teacherDetails();
    Teacher teacher =  ServiceDataSource.teacher();
     
    UserByUsername userByUsername = new UserByUsername
    {
        Username = teacher.Name,
        Id       = teacher.Id
    };
     
    _userAPIRepository.Setup(x => x.GetUserIdsByName(userByUsername)).Returns(Task.FromResult(teacherDetails);
            
     
    var result = await _userServiceAPI.GetTeacherDetails(teacher);
     
    //Assert
    Assert.True(result.Count > 0);
}

Answer 1

当参数设置与执行测试时传入的参数不匹配时，模拟 returns 默认为 null。在呈现的案例中，使用了一个实际的 instance/reference，它与在测试对象中创建的实例不匹配。

使用参数匹配器从模拟中获取所需的行为，因为参数是在被测对象中初始化的。

[Fact()]
public async Task GetUserDetails() {
    //Arrange
    List<TeacherDto> teacherDetails = ServiceDataSource.teacherDetails();
    Teacher teacher =  ServiceDataSource.teacher();
     
    _userAPIRepository
        .Setup(x => x.GetUserIdsByName(It.Is<UserByUsername>(u => 
            u.Username == teacher.Name && u.Id == teacher.Id)))
        .ReturnsAsync(teacherDetails);
            
    //Act         
    var result = await _userServiceAPI.GetTeacherDetails(teacher);
     
    //Assert
    Assert.True(result.Count > 0);
}

注意使用 It.Is<> 添加具有特定 filter/predicate 的参数匹配器。

如果不需要实际匹配成员而只接受任何UserByUsername，则可以使用It.IsAny<>代替

例如

[Fact()]
public async Task GetUserDetails() {
    //Arrange
    List<TeacherDto> teacherDetails = ServiceDataSource.teacherDetails();
    Teacher teacher =  ServiceDataSource.teacher();
     
    _userAPIRepository
        .Setup(x => x.GetUserIdsByName(It.IsAny<UserByUsername>()))
        .ReturnsAsync(teacherDetails);
            
    //Act         
    var result = await _userServiceAPI.GetTeacherDetails(teacher);
     
    //Assert
    Assert.True(result.Count > 0);
}

参考 Moq Quickstart 以更好地了解如何使用该库

模拟存储库返回 null

Mock repository is returning null

c#

unit-testing

moq

asp.net-core

asp.net-core-webapi