public class MathRoundTests : Linq3IntegrationTest
{
    [Fact]
    public void Math_round()
    {
        var collection = CreateCollection();

        var query = collection.AsQueryable()
            .Where(i => Math.Round(i.A) == 10);

        var results = query.ToList();

        results.Should().OnlyContain(i => Math.Round(i.A) == 10);
    }

    private IMongoCollection<Data> CreateCollection()
    {
        var collection = GetCollection<Data>("test");
        CreateCollection(
            collection,
            new Data { A = 10.234 },
            new Data { A = 9.6 },
            new Data { A = 9.2 },
            new Data { A = 5.42 });
        return collection;
    }

    private class Data
    {
        public double A { get; set; }
    }
}