Extending Selenium server with custom commands

In this posting I document extending Selenium server with a custom javascript method, getAllRadios(), to return all radio button elements in a page. It’s based on the getAllButtons() that is stock in Selenium.

I will demonstrate two ways to add this custom method. The first strategy is to add the custom method to the native javascript files that ship with Selenium server. This is not the recommended way to extend Selenium but it is an almost guaranteed way to be sure the server picks up my new method and that frees me to focus on getting my client syntax right for calling the new method using the client’s doCommand() method.

Method 1 – selenium-browserbot.js + selenium-api.js

Unpack the server jar into a temporary directory to get access to the selenium-browserbot.js and selenium-api.js files.

[20:54 20090906 crashing@server /selenium-server-1.0.1/temp]
$ jar xf ../selenium-server.jar

The new custom method is added to core/scripts/selenium-browserbot.js. It is a slightly modified version of getAllButtons() which is defined in the same file.

BrowserBot.prototype.getAllRadios = function() {
var elements = this.getDocument().getElementsByTagName('input');
var result = [];
for (var i = 0; i < elements.length; i++) {
if (elements[i].type == 'radio') {
result.push(elements[i].id);
}
}
return result;
};

and then the new method is exposed to the Selenium API in core/scripts/selenium-api.js, again modeling after getAllButtons() in selenium-api.js.

Selenium.prototype.getAllRadios = function() {
return this.browserbot.getAllButtons();
};

Now rebundle the updated javascript into a new server jar, replacing the original.

[21:01 20090906 crashing@server /selenium-server-1.0.1/temp]
$ jar cmf META-INF/MANIFEST.MF ../selenium-server.jar .

Method 2 – user-extension.js

The better way to extend Selenium is to add methods to the user-extensions.js file. This avoids screwing around with the native server jar. I initiall had some trouble getting this working, hence the Method 1 approach, but after a bit of futzing I finally got this to work.

Selenium.prototype.getAllRadios = function() {
var elements = this.browserbot.getDocument().getElementsByTagName('input');
var result = [];
for (var i = 0; i < elements.length; i++) {
if (elements[i].type == 'radio') {
result.push(elements[i].id);
}
}
return result;
};

This is basically the same method used in selenium-browserbot.js. The important changed bits are (1) the method is attached to the Selenium object instead of the BrowserBot (Selenium.prototype rather than BrowserBot.prototype) and (2) calling getDocument() on the browserbot instance.

I start the Selenium server with the -userExtensions option pointing to the user-extensions.js file.

java -jar \
/selenium-server-1.0.1/selenium-server.jar \
-userExtensions /user-extensions.js

Client Coding

For either of the above methods of extending the Selenium server, I call this new method in my client code with the doCommand().

/** incomplete code **/

proc = new HttpCommandProcessor(seleniumServerHost,
seleniumServerPort, brower, seleniumServerStartUrl);
selenium = new DefaultSelenium(proc);

selenium.open(url);

// radio buttons returned as comma-delimited strings
String allRadios = proc.doCommand("getAllRadios", null);

// alternatively, get radio buttons as a String array
String[] radios = proc.getStringArray("getAllRadios", null);
for (String radio : radios) {
System.out.println(radio);
}

To call custom doCommand()‘s, it’s necessary to instantiate with DefaultSelenium(proc) to inject the HttpCommandProcessor into the DefaultSelenium object.