Unit testing

Tichaona J

Just watching this VSTS 2008 Unit Testing 1 of 1 lets you know how to test methods that return something, my question here is how do you test methods in Visual Studio 2008 that don't return any value? For example:

private void BtnLoad_Click(object sender, RoutedEventArgs e)
{
//Declare a new file dialog box
OpenFileDialog dlg = new OpenFileDialog();

        //Set properties for the dialog...
        dlg.Title = "Select one or more media files";
        dlg.Multiselect = IsEnabled;
        dlg.Filter = "Media files(\*.mp3;\*.wav;\*.wma;\*.avi;\*.mp4;\*.mpg;\*.wmv)|\*.mp3;\*.wav;\*.wma;\*.avi;\*.mp4;\*.mpg;\*.wmv|All files(\*.\*)|\*.\*";

        //The result of the open file dialog is either true or false (didn't work).
        Nullable<bool> result = dlg.ShowDialog();

        //If the result of the open file dialog was true then....
        if (result == true)
        {
            string\[\] files;

            files = dlg.FileNames;

            //Add each file into the list box
            foreach (string file in files)
            {
                lstBxList.Items.Add(file);
            }                
        }

    }

fjdiewornncalwe

You're trying to run an automated test on against a UI method. I may simply be a little old-school, but I typically don't write unit tests against UI methods because of the interaction required.

I wasn't, now I am, then I won't be anymore.

Dave Kreskowiak

Your code is incorrectly written. This is a UI event handler and the code that you hav in it DOES return a value. This dialog box code should be in its own method that returns a fully qualified path to the caller. It should NOT be sitting inside an event handler. You also wouldn't run a unit test against a method that requires user interaction. Another question. Why on earth would you use a nullable boolean to get the return value of a dialog box? It's either going to return true or false, never null. So, what's the point?

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Dave Kreskowiak

Tichaona J

Right I see what your saying...First of all I should have pointed out that I am working with WPF hence use a nullable boolean to get the return value of a dialog box, the other way of calling a dialog box does not seem to work when developing a WPF based app. Secondly I used this as am example which I have to say after the response I got from fock was a bad example of which I was hoping fock would use it to illustrate how to test a method that does not return anything...Please bear in mind that I am a rooky,so if I say something that seems obvious to you, may not be the case with me...

Pete OHanlon

Dave Kreskowiak wrote:

Why on earth would you use a nullable boolean to get the return value of a dialog box? It's either going to return true or false, never null. So, what's the point?

Actually, it should return a DialogResult. The use of a bool condition would indicate that it's a WPF/SL dialog box, and this does return a nullable boolean condition.

I have CDO, it's OCD with the letters in the right order; just as they ruddy well should be

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Dave Kreskowiak

I haven't done any WPF until very recently, and nothing on dialogs yet, so my ignorance is showing through there. :-D

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Dave Kreskowiak

David Ewen

As defined that method can not be unit tested as it requires user input (to select the file). But as you want an example on how to test a method that doesn't return a value it can be refactored slightly as below. To test a method that returns void you test for the change in system state that the method call is meant to impose. In this case the listbox should contain 2 items after the call, granted testing if items were added to a listbox is of dubious benefit but this is just for illustrative purposes.

private void BtnLoad_Click(object sender, RoutedEventArgs e)
{
//Declare a new file dialog box
OpenFileDialog dlg = new OpenFileDialog();

//Set properties for the dialog...
dlg.Title = "Select one or more media files";
dlg.Multiselect = IsEnabled;
dlg.Filter = "Media files(\*.mp3;\*.wav;\*.wma;\*.avi;\*.mp4;\*.mpg;\*.wmv)|\*.mp3;\*.wav;\*.wma;\*.avi;\*.mp4;\*.mpg;\*.wmv|All files(\*.\*)|\*.\*";

//The result of the open file dialog is either true or false (didn't work).
Nullable<bool> result = dlg.ShowDialog();

//If the result of the open file dialog was true then....
if (result == true)
{
	LoadFilesToListbox(dlg.FileNames);
}

}

public void LoadFilesToListbox(string[] files)
{
//Add each file into the list box
foreach (string file in files)
{
lstBxList.Items.Add(file);
}
}

[TestMethod]
public void TestLoadFilesToListbox()
{
LoadFilesToListbox(new string[] { "file1.txt", file2.dat" });
Assert.AreEqual(2, lstBxList.Items.Count);
}