Friday, August 21, 2009

A Quick Look at Tellurium

Tellurium builds on top of Selenium to present a more object-oriented abstraction, potentially resulting in more maintainable test code, and perhaps even making it easier to construct the tests to begin with; both of these things would require more familiarity on my part to judge fairly.

While Tellurium provides an IDE (TrUMP), it is not used for the same purpose as the Selenium IDE - i.e. rather than click-and-record of sequential events, it facilitates click-and-generate of (Groovy) code snippets for a given UI component or hierarchical collection of components. These become the basis of so-called "UI Module" classes, to which the developer can add methods that access the UI component. Test classes - whether in TestNG, Junit, Groovy, etc. - then leverage that set of methods to write test cases. This approach encapsulates the complex lookup (XPath, etc.) needed around UI components with access methods around those components, and supports separating the concerns of UI component vs tests written against that component. This of course sets the stage for reuse of the UI components in different test classes. Since Tellurium provides a relative location lookup model, it insulates the test cases against changes to the UI (i.e. an absolute XPath expression could break if any of the enclosing path components changes, e.g. when the UI is laid out differently).

Good Things and Random Notes

Most notably, Tellurium provides an OO approach. This is good for quick construction of test code and, more importantly, ease of maintenance on that codebase over time.

As a convenience wrapper around Selenium, Tellurium starts up the Selenium server automatically when one runs a test case.

To use TrUMP, the Tellurium IDE, SSL must be turned off; this is however probably a good idea anyway for testing purposes. The IDE is used by turning Record on, clicking on one or more UI components (e.g. a form, a table, link, etc.), and then clicking on Generate in the IDE. This (ultimately) produces a set of snippets, with any components that are part of a hierarchy in the page represented as such. Each snippet presents all attributes in the given component; you can next proceed to customize things (include/exclude snippets, rename for better abstraction, etc.). Next, you'd export the snippets to a Groovy class that represents the given UI Module, and as mentioned add methods to support access by test classes.

One roadblock that took some time to solve was dealing with iframes; the browser instance became confused, losing track of its connection to Tellurium. To deal with this type of thing, set useMultiWindows = true in the TelluriumConfig.groovy file.

When things go wrong - i.e. unexpected failures in your test case - a screenshot is automatically saved to facilitate revisiting things in a post-mortem.


As of this writing, TrUMP is not compatible with Firefox 3.5.2; I don't know yet about other 3.x releases.

The export to Groovy is a heavy-handed "save as file" approach; I would prefer just a quick export-to-window-in-TrUMP model so I could more quickly copy-and-paste into my IDE.

I had no luck using TrUMP to capture webpage elements that were generated by post-processing AJAX, i.e. links constructed dynamically by JavaScript based on the data returned. Nor did I succeed with TrUMP in capturing Dojo menus that appear from dropdown buttons (a typical Dojo approach). In both of these cases I had to do things manually, using various approaches like Selenium, FireBug "Inspect" (in particular leveraging the Search functionality in 3.5), and old-fashioned examination of the page source. The good news is that once a particular UI component's location has been fleshed out, that effort is reusable since the resulting UI module is reusable.

While Tellurium provides an OO approach - which IMO is a Good Thing - there are as such some (not unreasonable) assumptions around just what behaviors certain objects should have. For example, it's not uncommon in Dojo widgets to find onclick event handlers (moreless) attached to TD tags; but from an OO point of view, a TD should not be clickable. This appeared to be show-stopper until I (quite by accident) stumbled on an attribute that could be retrofitted to a UI module component description that instructs it to "respond" to click events (i.e. add respond:["click"] to the generated Groovy UI Module description).

The "quite by accident" serendipity described above should be better; in fairness, Tellurium is a nascent product, but I hope that soon some first-class JavaDoc and other reference documentation is provided (or, it could be that I just need to poke around more; but, again, this shouldn't take any effort at all to find - it "should" just jump out at me).


All in all, I'm giving a qualified two thumbs up. Tellurium out-of-the-gate shows great potential, and I personally prefer it to Selenium. It's moreless the kind of thing that I'd probably have ended up doing myself to get the level of abstraction I'd want; I'm grateful to the folks at Google to have done it for me.

There is still a great deal of facility I've yet to explore with this tool. It appears to have a fair amount of power, and I look forward to writing up more insights and tips around Tellurium.

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