如何模拟使用 Moq 对此 C# 代码进行的以下 DBContext 调用？

Question

当在用 C# 编写的服务文件中遇到以下行时，我在使用 Moq 运行单元测试时遇到问题。任何关于如何模拟这个特定调用的有价值的输入都将在这里受到赞赏。谢谢。这里 _context 是 DBContext 的实例。

var dataObj = _context.FromSqlNotRequired(query, commandParameters).rows;

单元测试设置：

 private readonly Mock<P4IDBContext> _mockContext;
        private readonly Mock<DbSet<MetricsCalibrated>> _metricsCalibratedMockSet;
        private readonly Mock<DbSet<FilterResult>> _filterMockSet;   
        private readonly MetricsService _metricsService;
        private readonly Mock<IMetricsService> metricsService;
        private readonly Mock<Dictionary<String, String>> _dictionary;
        private readonly SourceDataController controller;

        //[Fact()]
        public MetricsServiceTests()
        {
            metricsService = new Mock<IMetricsService>();
           
            controller = new SourceDataController(metricsService.Object);
            _metricsCalibratedMockSet = new Mock<DbSet<MetricsCalibrated>>();
            _metricsCalibratedMockSet.Setup(m => m.AsQueryable()).Returns(_metricsCalibratedData);
            _dictionary = new Mock<Dictionary<String, String>>();
            _filterMockSet = new Mock<DbSet<FilterResult>>();
            _filterMockSet.Setup(m => m.AsQueryable()).Returns(_filterData);
            var commandParameters = new Dictionary<string, string>();
            _mockContext = new Mock<P4IDBContext>();
            
            _mockContext.Setup(m => m.MetricsCalibrated).Returns(_metricsCalibratedMockSet.Object);
            _mockContext.Setup(m => m.FilterResult).Returns(_filterMockSet.Object);
            _metricsService = new MetricsService(_mockContext.Object);

        }

错误 - 消息：

Message: 
    System.NullReferenceException : Object reference not set to an instance of an object.

  Stack Trace: 
    RelationalDatabaseFacadeExtensions.GetFacadeDependencies(DatabaseFacade databaseFacade)
    RelationalDatabaseFacadeExtensions.GetDbConnection(DatabaseFacade databaseFacade)
    DbContextExtensions.FromSqlNotRequired[T](DbContext context, String strSQL, Dictionary`2 commandParameters) line 24
    MetricsService.GetBasicData(String wherePart, IDictionary`2 selectedDict, String timeInterval, Dictionary`2 commandParameters, String tillDate) line 242
    MetricsService.GetFilteredData(FilterOptions options) line 64
    MetricsServiceTests.TestGetFilteredData() line 63

Answer 1

[Fact]
public void Test()
{ 
    //Below is the setup part. 
    //given  
    var metricsCalibratedData = new List<MetricsCalibrated>
        {
            new MetricsCalibrated{ /* ... */ }, /// fill sample data
            new MetricsCalibrated{ /* ... */ }
        }.AsQueryable();

        var mockMetricsCalibratedSet = new Mock<DbSet<MetricsCalibrated>>();
        mockMetricsCalibratedSet .As<IQueryable<MetricsCalibrated>>().Setup(m => m.Provider).Returns(metricsCalibratedData.Provider);
        mockMetricsCalibratedSet .As<IQueryable<MetricsCalibrated>>().Setup(m => m.Expression).Returns(metricsCalibratedData.Expression);
        mockMetricsCalibratedSet .As<IQueryable<MetricsCalibrated>>().Setup(m => m.ElementType).Returns(metricsCalibratedData.ElementType);
        mockMetricsCalibratedSet .As<IQueryable<MetricsCalibrated>>().Setup(m => m.GetEnumerator()).Returns(metricsCalibratedData.GetEnumerator());

   var filterResultData = new List<FilterResult>
    {
        new FilterResult{ /* ... */ },
        new FilterResult{ /* ... */}
    }.AsQueryable();

    var mockFilterResultSet = new Mock<DbSet<FilterResult>>();
    mockFilterResultSet.As<IQueryable<FilterResult>>().Setup(m => m.Provider).Returns(filterResultData .Provider);
    mockFilterResultSet.As<IQueryable<FilterResult>>().Setup(m => m.Expression).Returns(filterResultData .Expression);
    mockFilterResultSet.As<IQueryable<FilterResult>>().Setup(m => m.ElementType).Returns(filterResultData .ElementType);
    mockFilterResultSet.As<IQueryable<FilterResult>>().Setup(m => m.GetEnumerator()).Returns(filterResultData .GetEnumerator());

    var mockContext = new Mock<P4IDBContext>();
    mockContext.Setup(c => c.MetricsCalibrated).Returns(mockMetricsCalibratedSet.Object);
    mockContext.Setup(c => c.FilterResult).Returns(mockFilterResultSet.Object);

   var sut = new MetricsService(mockContext.Object);
  // Now, the test can b run

  var actualResult = sut.GetFilteredData(validFilterOptions);

  // Then Assert...