测试对象具有以下构造函数

/// <summary>
    /// Initializes a new instance of the <see cref="CsvFileRepository{TModel}"/> class.
    /// </summary>
    /// <param name="fileService">The file service.</param>
    /// <param name="repositorySettings">The repository settings.</param>
    /// <param name="mappingFunction">The mapping function. The mapping function takes in a line from the CSV file and returns the model for said line.</param>
    public CsvFileRepository(IFileService fileService,IRepositorySettings repositorySettings,Func<string,TModel> mappingFunction)
    {
        this.FileService = fileService;
        this.RepositorySettings = repositorySettings;
        this.MappingFunction = mappingFunction;
    }

我已经创建了一个测试存根,如下所示：

public class when_i_pass_a_csv_file_the_results_are_mapped_to_model_objects : WithSubject<CsvFileRepository<StandardOffer>>
{
    Establish context = () => With(new OffersInFile(new[] { OfferTestData.BobsCsvTestData,OfferTestData.JohnsCsvTestData }));

    Because of = () => result = Subject.Get();

    It should_return_the_same_number_of_fruits_as_there_are_in_the_source_repository = () => result.Count().ShouldEqual(2);

    static IEnumerable<IOffer> result;                            
}

但我不知道如何告诉Machine.Fakes使用Func mappingFunction参数的特定值.