11 April 2024 Leave a comment Tech-Help
GUI testing is an integral part of software development, ensuring that user interactions with an application are functioning as expected. In Delphi, GUI testing can present certain challenges, particularly when dealing with modal forms. Modal forms, by design, pause the code execution until the form is closed, which can interrupt automated testing scripts. This article provides a guide on how to test modal forms within Delphi applications effectively.
Understanding Modal Forms in Testing
When a modal form is displayed using the ShowModal method, it initiates a secondary message loop that does not exit until the form is closed. This behavior causes automated test case code to ‘pause’, waiting for user interaction, which is not ideal for GUI testing scenarios.
Testing Modal Forms Non-Modally
To continue with automated testing without manual intervention, modal forms need to be tested in a non-modal state. Here’s how you can achieve this:
- Show the usually modal form using the
Showmethod instead ofShowModal. This allows your test case code to continue executing and simulate user actions on the form. - Since the form is shown non-modally, the
ModalResultproperty will not close the form. You can simulate user actions, such as clicking the “Ok” button, and then check if theModalResultis set correctly.
Injecting Show Commands for Testability
To test code that inherently calls ShowModal, such as displaying an error dialog, you need to make your “show commands” injectable. This technique involves using dependency injection to allow for a mock implementation during testing, which does not pause the test execution.
Steps to Implement Injectable Show Commands:
- Define an interface (or abstract base class) for displaying error messages. For instance:
- Have the form under test hold a reference to this interface and use it to show errors when needed.
- For production code, use a default implementation of this interface that displays messages as usual.
- During testing, inject a mock implementation that prevents the form from pausing the test and allows you to verify that the correct error message is generated.
- Enhance the mock implementation to verify the correct message text:
IErrorMessage = interface
procedure ShowError(AMsg: String);
end;
procedure TForm1.OnOkClick;
begin
if (Edit1.Text = '') then
FErrorMessage.ShowError('Please fill in your name');
else
ModalResult := mrOk;
end;
procedure TTestClass.TestValidationOfBlankEdit;
begin
Form1.Show; //non-modally
Click('OkButton');
CheckEquals(0, Form1.ModalResult);
end;
TMockErrorMessage = class(TInterfacedObject, IErrorMessage)
private
FLastErrorMsg: String;
protected
procedure ShowError(AMsg: String);
public
property LastErrorMsg: String read FLastErrorMsg;
end;
Conclusion
By showing modal forms non-modally and injecting show commands, you can effectively test GUI components in Delphi that would otherwise halt automated test execution. This approach allows for a more seamless and continuous testing process, ensuring that your application’s user interface behaves as expected even when modal dialogs are involved.
