libcvautomation: Writing Application Tests

Author:: Bradlee Speice <bspeice@uncc.edu>

Date:: 7/18/2012

Audience

This document was written for people with some intermediate knowledge of BASH.
Screenshot experience is required - being able to create screenshots of windows using GIMP, the import command from ImageMagick, or something similar.
Required for working with libcvautomation internals (not needed strictly for writing application testing):
- Intermediate-level C knowledge required for interfacing with libcvautomation. There isn't much complicated going on with libcvautomation itself, but you need to know to use cvaOpenDisplay() for grabbing a display and then cvaCloseDisplay() for closing it later for example.
- C++ is available, but currently only as extern "C" style bindings.
- Python bindings are in progress as of time-of-writing

Purpose

This document is intended to outline the libcvautomation testing library for GUI applications and its two reference programs cva-match and cva-input
These programs allow you to automate mouse and keyboard events in response to what appears on screen - for example, clicking a button based on an image of that button on screen.

Using Libcvautomation

Since libcvautomation is a shared-object library intended to bundle a lot of functionality in one area, we must use external programs to agin access to the functions of libcvautomation.
Two reference programs have been included to make this easy - cva-match and cva-input
The reference programs are fairly full-featured, and expose most of libcvautomation:
- cva-match allows you to match multiple image files against a root image providing very fine control over how specific the match is
- cva-input allows you to drive the X11 server using the XTest extension - for example, clicking on a button from image, clicking a key on the keyboard, and more.
These two programs should implement all functionality needed for GUI automation. Please contact bspeice@uncc.edu if you have suggestions for extra functionality, patches, comments, etc.
Finally, if you want to write your own programs using libcvautomation, the headers are located on your system. Use:
```
 #include <libcvautomation/libcvautomation.h> 
```
to include all necessary header files. See the "Files" tab above to get an idea of what functionality exists.
Note:
Intermediate C or C++ knowledge is required for programming with libcvautomation. C++ is currently only supported through extern "C", and full C++ bindings are not currently planned. Libcvautomation itself is incredibly simple, but interfaces with a few API's (Xlib, libcv) that it is helpful to have an idea of how to use.

Application Testing

Now we get into the good stuff. The basic process for application testing is as follows:

Create a sequence of screenshots for all mouse-clicks
Create a testing wrapper in BASH for automating the application
Test the wrapper and tune any necessary options

Creating the Screenshot Sequence

This process creates a set of screenshots by which libcvautomation can drive the X11 server
The process is simple - create a screenshot of all buttons you would like to click in an application test, or location where you would like to move the mouse, etc.
This can be accomplished a number of different ways - using GIMP, the import command, or any other screenshot program. Additionally, libcvautomation will support any image format that OpenCV does. At the time of writing, these are:
- Windows bitmaps - *.bmp, *.dib
- JPEG files - *.jpeg, *.jpg, *.jpe
- JPEG 2000 files - *.jp2
- Portable Network Graphics - *.png
- Portable image format - *.pbm, *.pgm, *.ppm
- Sun rasters - *.sr, *.ras
- TIFF files - *.tiff, *.tif
Some tips on creating screenshots:
- Use as distinct an image as possible in a screenshot. For example, the following images look very similar, but can do very different things:
  - The large amount of grey-space in each of the images can be very confusing. While the text itself is different, the overwhelming amount of grey space can result in a false positive. Limiting the space of the screenshot can be useful:
  - Limiting the button size in this case helps the program identify what button you want to click, but in general you want to include as much detail as possible.
- Be careful of where an image may appear multiple times in a screenshot. For example, a "Help" button on a dialog may get confused with the "Help" menu at the top of the screen.

Create a Testing Wrapper

This is where the BASH knowledge comes into play. We are going to write a script that will run your application test, to make sure that the GUI is functioning correctly.

The following is the (strongly) recommended process, but is not strictly necessary to follow this. The way I'm going to explain this is by giving an example test I wrote, and explain what is going on:

 #!/bin/bash
 #This is an application test involving libcvautomation and libreoffice
 . /usr/local/etc/libcvautomation_funcs

 #Changing any wrapper parameters should go here


 start_libreoffice_writer ()
 {
    click_i "screens/gnome-1_menu.png" "screens/kde-1_menu.png" && sleep 1
    click_i "screens/gnome-2_officeMenu.png" "screens/kde-2_officeMenu.png" && sleep 1
    hover_i "screens/gnome-3_LibreOfficeWriter.png" "screens/kde-3_LibreOfficeWriter.png"
    jiggle_mouse
    click
    sleep 30
 }

 close_libreoffice_writer()
 {
    click_i "screens/gnome-4_fileMenu.png" "screens/kde-4_fileMenu.png" && sleep 1
    click_i "screens/gnome-5_fileExit.png" "screens/kde-5_fileExit.png" && sleep 1
    click_i "screens/gnome-6_discard.png" "screens/kde-6_discard.png" && sleep 1
 }

 start_libreoffice_writer
 close_libreoffice_writer

 #!/bin/bash
 #This is an application test involving libcvautomation and libreoffice
 . /usr/local/etc/libcvautomation_funcs
 #Changing any wrapper parameters should go here

The purpose of these lines is just the standard BASH header. Additionally, we import a wrapper created for libcvautomation to make our job easier. Please note that this is the default directory for the wrapper, your installation may be different. Use the command locate libcvautomation_funcs to find it on your computer. The wrapper itself is a handful of macros used to make our job easy.

Changing any wrapper parameters should go after sourcing the wrapper functions. See below on Testing the Testing Wrapper for more information.

 start_libreoffice_writer ()
 {
    click_i "screens/gnome-1_menu.png" "screens/kde-1_menu.png" && sleep 1
    click_i "screens/gnome-2_officeMenu.png" "screens/kde-2_officeMenu.png" && sleep 1
    hover_i "screens/gnome-3_LibreOfficeWriter.png" "screens/kde-3_LibreOfficeWriter.png"
    jiggle_mouse
    click
    sleep 30
 }

This is the actual body of work done by libcvautomation
click_i is a function to click the mouse at an image - in this case, the gnome or kde menu.
- Because of how the cva-input program is designed, you can give it multiple images, and it will only select the one currently available. See Testing the Testing Wrapper for more information on how to use this (TOLERANCE specifically)
- By using the function click_i, we make things a bit more readable - the full command line is cva-input -s 'icmouseclick <filename>'
- See Appendix of Wrapper Functions for a list of all functions available in the wrapper.
hover_i is a function to move the mouse to an image - in this case, move it over the LibreOffice menu item.

Then we jiggle the mouse to make sure that the item activates, click, and wait for the program to start up.

 close_libreoffice_writer()
 {
    click_i "screens/gnome-4_fileMenu.png" "screens/kde-4_fileMenu.png" && sleep 1
    click_i "screens/gnome-5_fileExit.png" "screens/kde-5_fileExit.png" && sleep 1
    click_i "screens/gnome-6_discard.png" "screens/kde-6_discard.png" && sleep 1
 }

Use the click_i function to close down LibreOffice writer - Find the "File" menu, click "Exit", and then make sure to discard all changes.
```
 start_libreoffice_writer
 close_libreoffice_writer
```
Actually run the functions given.
Please note that this is a fairly trivial example. The full list of commands available in the wrapper is given in Appendix of Wrapper Functions

Testing the Testing Wrapper

First things first, run through the testing wrapper to make sure that everything is O.K.
If you need to, some things you can do to tune the application test are as follows:
- Set the SEARCH_METHOD
  - This value adjusts how libcvautomation searches for sub-images. See Libcv Search Methods for more information on accepted values, and how each works.
- Set the TOLERANCE
  - This value adjusts how strict libcvautomation is when trying to find a sub-image. See Libcv Search Methods for more information on how to control how libcvautomation searches for images.
- Set USE_SANE_TOLERANCE
  - This value implements a more sane way of setting the tolerance value - Where normally the tolerance ranges from INT_MIN to INT_MAX, the sane tolerance accepts values of 1 - 100 ( $ 1 \approx 0 $, and $ 100 \approx INT\_MAX $)
  - To enable sane tolerance, set:
```
 USE_SANE_TOLERANCE="<any_value>" 
```
  - To disable sane tolerance (the default) set:
```
 USE_SANE_TOLERANCE="" 
```
  - Set USE_CENTER
    - By default, the wrapper will use the center of an image as opposed to the upper-left corner to click on. To disable this behavior, set:
      USE_CENTER=""
    - To set the behavior back to using center-based matching, set:
      USE_CENTER="<any_value>"
  - Set the OUTFILE and ERRFILE
    - The application wrapper logs a whole lot of information about what it does to make debugging easy. However, to make sure that you're not overwhelmed by the output, the wrapper also directs the output to /dev/null by default.
    - To redirect the output of OUTFILE and ERRFILE, set them to any file you want. For example, the following code will create a temporary file for OUTFILE and ERRFILE, and notify you of what they are:
      OUTFILE=`mktemp` ERRFILE=`mktemp` echo "OUTFILE location: $OUTFILE" echo "ERRFILE location: $ERRFILE"
- A full list of commands provided by the wrapper is available at Appendix of Wrapper Functions
Note:
These options are controlled using the testing script as demonstrated above. Any modifications to the following values should be done at the line:
```
 #Changing any wrapper parameters should go here 
```

Wrapping Up

At this point you should have all the information you need to write your own application tests. The libcvautomation library and reference programs were designed to be simple and powerful, but if you invest the time to learn them and some expert BASH scripting, you can do some very complex things.
- For example, integrating a Test Anything Protocol wrapper into your scripts as well.
If you have questions, comments, concerns, suggestions, or feedback in general, feel free to let me know at bspeice@uncc.edu.