Grid is a fast and versatile component of GXT. Testing it with Selenium is quite simple but requires couple points to be handled. After some thinking and experimenting I came up with following.

First of all, you will need Firebug or similar tool to inspect DOM created by GXT. A suitable example of Grid is http://extjs.com/examples/grid/grid.html. Simply open that URL and open your Firebug.

We are interested to check that Nokia's stock symbol matches NOK. By inspecting the symbol column cell for Nokia we see something like this:

<div class="x-grid3-cell-inner x-grid3-col-symbol">NOK</div>

We can use the 'x-grid3-col-symbol' as a CSS locator. The syntax in IDE is then 'css=div.x-grid3-col-symbol'. This selects the column but the we should also specify the row.

This can be done by creating a new class extending GridViewConfig and overriding getRowStyle method. This method should return suitable value (for example name from Model). You might want to add a postfix or prefix to the value to avoid conflicts. The value becomes part of the CSS style for the row. Set your own instance extending GridViewConfig to your Grid's using myOwnGrid.getView().setViewConfig() method.

Now you should be able to pin point a specific cell using Selenium locator with two CSS classes: 'css=div.x-grid3-col-symbol div.row_nokia'