Gets or sets a value indicating whether this control is running in the context of Visual Studio's UserControl Test Container.
true when run in the test container; otherwise, false. The default is false.
By (my) convention, this property may be manually set within the UserControl Test Container to signal the parent control to expose additional functionality that allows the parent control to be tested in isolation, without having to embed it in an application. In this case, setting it to true makes a Step button visible that lets the user engage the methods of this control.
ProgressBarMessager Class | CleanCodeControls.Forms Namespace