bisen2/winforms-stress

Stress testing the WinForms UI update cycle

Winforms Stress Testing

Stress Test Breakdown

This repo contains code that I am using to stress test the UI update loop of WinForms applications.

This project contains three types of tests:

• Invoke tests
• BeginInvoke tests
• Irregular BeginInvoke tests

Invoke Tests

These tests call Invoke(delegate) on a form repeatedly from a different thread. This should not actually provide much stress to the UI thread as Invoke(...) is a blocking call, meaning that the non-UI thread is unable to call Invoke(...) again until the UI has finished the work specified in the first call.

BeginInvoke Tests

These tests call BeginInvoke(delegate) on a form repeatedly from a different thread. Depending on the frequency of BeginInvoke(...) calls, this can provide a lot of stress to the UI thread. The initial round of testing has shown that the UI thread can handle up to 1,000 calls/second, but beyond that freezes up and becomes unresponsive.

Irregular BeginInvoke Tests

These tests call BeginInvoke(delegate) in a similar manner to the BeginInvoke tests, but occasionally skips the normal pause between BeginInvoke(...) calls. This is done to test how the UI thread responds to occasionally quick BeginInvoke(...) calls when the average speed is still slow. The initial round of testing has shown that the UI thread can handle occasional BeginInvoke(...) calls that come in with less than 1ms delays, so long as the overall rate of incoming calls does not exceed 1,000 per second.

Project Structure

This project is composed of three source files: Program.fs, TestRunner.fs, and Types.fs.

Types.fs

This file contains the low level implementation of the tests. The Forms module contains a type MyForm, which defines the form that invoke requests are made against. This type provides the methods for updating UI elements that will be called during tests. This file also contains the Stressor module, which provides functions that accept a form and delegate as input and set up the non-UI thread to ping invoke requests against the form. Each function in this module represents a different way in which invoke requests can be pushed onto the UI thread.

TestRunner.fs

This file provides the suite of tests that can be run using the types defined in Types.fs. The GenericTest module provides a higher level abstraction over the Stressor module by setting up the form and the stressor, running them in parallel, and then asking the user to report the visual experience of the form. The Tests module builds on top of this abstraction by providing functions that define a specific form and delegate to the tests. The Tests module is simply specified implementations of the GenericTest functions that define the scope of the available test suite. Finally, the TestRunner module provides a function that runs the entire test suite sequentially and builds a chart of the collected data.

Program.fs

This is the entry point of the application. It sets the test parameters, uses the TestRunner module to run the entire test suite, and then displays the chart for the user.