Unit test for Expression tree in c#

Question

How do I write a unit test for a Expression tree in C#.

I have this class which needs to be tested. This method returns a Expression tree and also gets one as a parameter.

code:

public ExpressionStarter<SpecFinderDataModel> DoSearch(bool status, string searchValue, ExpressionStarter<SpecFinderDataModel> predicate)
{
    var localPredicate = predicate;
    if (status == false)
    {
        var searchTerms = searchValue.Split(' ').ToList().ConvertAll(x => x.ToLower());
        localPredicate = localPredicate.Or(s => searchTerms.Any(srch => s.ProductID.ToLower().Contains(srch)));
        localPredicate = localPredicate.Or(s => searchTerms.Any(srch => s.ISBN13.ToLower().Contains(srch)));
        localPredicate = localPredicate.Or(s => searchTerms.Any(srch => s.Title.ToLower().Contains(srch)));
    }
    return localPredicate;
}

Any advice would be helpful. Thanks.

Update #1 I have used LinqKit for ExpressionStarter

Compile the result Expression to `Func` and verify the result with relevant input — Mrinal Kamboj, Jul 30 '18 at 07:01
The problem is I have written unit test for basic concepts, but not for advanced like using Expression. I have no idea. Could you please point me where to look? — Ranjith Varatharajan, Jul 30 '18 at 07:07

score 1 · Accepted Answer · answered Jul 30 '18 at 09:46

This shall be simple, though I will use the Expression<Func<SpecFinderDataModel,bool>> instead of LinqKit APIs, which is used internally, In the DoSearch method, you need Expression<Func<SpecFinderDataModel,bool>> as input, based on the method assuming following as the definition of the type SpecFinderDataModel

public class SpecFinderDataModel
{
    public string ProductID {get; set;}

    public string ISBN13 {get; set;}

    public string Title {get; set;}
}

Now you need to simply test various options, as done in regular unit test, a sample:

   // Initial Expression value constant false is the result
   Expression<Func<SpecFinderDataModel, bool>> expr = c => false;

    // SpecFinderDataModel Object
    var sfd = new SpecFinderDataModel
    {
     ISBN13 = "",
     ProductID = "Test A B C",
     Title = ""
    }

    // Call DoSearch and supply the sfd for testing
    var result = DoSearch(false,"Test",expr).Compile()(sfd);

    // Assert the result in the unit test to understand 
    Assert.True(result,true);

Like this based on combinations of the DoSearch parameters and test object sfd, you can create any number of unit test cases to test your code

You are awesome. it worked like a charm. Thank you @Mrinal – Ranjith Varatharajan Jul 30 '18 at 11:34 — Ranjith Varatharajan, Jul 30 '18 at 11:34
Welcome, glad it helped – Mrinal Kamboj Jul 30 '18 at 12:30 — Mrinal Kamboj, Jul 30 '18 at 12:30

Unit test for Expression tree in c#

1 Answers1