单元测试LINQ可枚举

Question

I am currently getting myself educated on unittests and LINQ, but I need some help.

What would be a correct way of unittesting methods like these:

    /// <summary>
    /// Returns the product of all numbers.
    /// </summary>
    static public decimal Product<TSource>(this IEnumerable<TSource> source, Func<TSource, decimal> selector)
    {
        return source.Aggregate<TSource, decimal>(1, (current, s) => current * selector(s));
    }

    /// <summary>
    /// Returns the product of all numbers.
    /// </summary>
    static public decimal? Product<TSource>(this IEnumerable<TSource> source, Func<TSource, decimal?> selector)
    {
        return source.Select(selector).Aggregate<decimal?, decimal?>(1, (current, i) => current * i ?? 1);
    }

I really couldn't figure out how. No matter what I keep trying; when running Code Coverage, a few blocks always stay uncovered.

What I have tried:

    [TestMethod]
    public void ExtendedProductAOfDecimalTest()
    {
        List<decimal?> items = new List<decimal?>(new decimal?[] { 5, 10, 15, 20, 25, 30 });
        Assert.AreEqual(11250000, Enumerable.Product(items, i => i));
    }

    [TestMethod]
    public void ExtendedProductBOfDecimalTest()
    {
        List<decimal> items = new List<decimal>(new decimal[] { 5, 10, 15, 20, 25, 30 });
        Assert.AreEqual(11250000, Enumerable.Product(items, i => i));
    }

Answer 1

I can see one part which would not execute. Because of your null coalescing operator '?? 1' You should also test null values:

List<decimal?> items = new List<decimal?>(new decimal?[] { 5, 10, 15, 20, 25, 30 , null});