Displaying Windows Forms inside unit test methods

Question

I just discovered unit test projects in Visual Studio .NET and am using test methods to set up examples of global code I have developed.

Some global methods involve displaying reusable dialogs like a date-picker and input box. Trouble is, sometimes forms will display and sometimes they won't.

I thought it was related to modality, because I have a report preview form that can be shown modally or non-modally. When I show that non-modally, it does not display. When I show it modally, it does.

Trying my input box never works:

string input = "";
using (InputBox box = new InputBox(Title, Prompt, Default))
{
    DialogResult result = box.ShowDialog();
    input = box.txtInput.Text.Trim();
}
return input;

Execution stops at the "box.ShowDialog()" line, and at that point I can inspect box and see that its dimensions, location, and visibility are all properly configured -- yet I cannot see the form. I've got to cancel the test to stop everything.

I'd love to use a unit testing project to act as a playground and showcase of existing code, but it seems very limited if I can't display certain forms. I realize this is not really what unit testing is meant for, but I hoped I could build a fun little sandbox this way to help get my developers up to speed.

Answer 1

I finally had some consistent success (and lack thereof) based on a single form property: ShowInTaskbar.

When a form had that property set to true, such forms would NOT display from a unit test method. When that property is false, all forms display. So, here are the rules as far as I know them to make sure a form can display from a unit test:

• The form should be created as a standard Windows Form item in the project.
• The form should have its ShowInTaskbar property set to FALSE.
• The form needs to be displayed modally (i.e. with ShowDialog()).

This has let me display and test all of my utility forms like date selectors and login screens.