BIRT reports can be tested on your favourite browser. Configure Eclipse for that:
Window > Preferences >General > General > Web browser:
The BIRT plugin also includes the BIRT runtime and the viewer. Click on the View Report button:
This will open a new borwser's window with the BIRT report. By default the viewer uses the framset mode with a menu with some actions on the top left and navigation bar on the tot right:
The BIRT report viewer can be performed in run mode by changing the URL on the browser. The menu is not displayed and all the data loaded into a single page:
Finally, you might want to configure the language for your reports (It can be done via URL parameters too):
Window > Preferences > Report Design > Preview