JavaScript unit testing in Visual Studio 2005

In my current project, we see an increasing use of JavaScript in our web application. Web 2.0, ya know. Hence, we have a growing need for being able to create automated JavaScript tests. A colleague of mine, Aslak Hellesøy, suggested that we should have a look at‘s unit test framework.

Fair enough, the unit test framework seemed to do the trick. We use both prototype and in our project, so the unit test framework seemed to fit in nicely. My next concern would be to make it as easy as possible for the developers to run the tests as well as integrating
it into our continuous integration builds (we use TFS). The test results should somehow be made available in the test run report. The steps needed to achieve this would be something like

  1. Write the JavaScript unit tests and place them in an HTML file
  2. From a Visual Studio Team System test method, fire up a browser that loads the HTML file and runs the test
  3. Fetch the result of the JavaScript unit tests and incorporate them into the test report provides the pieces for 1 and 2 above out of the box. It also supports POSTing the results back to a web server using Ajax. That could be an approach that would be a part of the solution for point 3 above. However, I felt that this approach is not an optimal solution. First of all because you would have to to
make the tests available thru a web server, the web server would need to receive the results, and store them somewhere. Then, the Visual Studio test would have to fetch the results and incorporate them. It all adds up to seem quite fragile. It is important that a test run has as few external dependencies as possible. Hence, I
wanted a separate approach. The browser should be able to load the JavaScript tests directly from the file system (file:///…). Then, after running the tests we should be able to traverse the DOM of
the HTML page directly to fetch the results.

As a result, we ended up with this approach:

  • Fire up Internet Explorer from .NET via its COM interface (Internet Explorer Object, SHDocVw.dll). You can find code for this here.
  • Load the file directly from the file system (file:///…) and execute the tests
  • Traverse the HMTL DOM to fetch the test results (using Microsoft HTML Object Library, mshtml.dll)
  • Report any error messages back using“…message…”)