There are tools available for visual regression testing of a webpage. Same tools can be used for OBIEE dashboards also.
The following open source tools are required:
CasperJS: Provides a set of APIs on top of PhantomJS that make working with web page forms, navigation etc.
PhantomJs: A headless browser, is the core functionality we’re using.
PhantomCSS: Provides the regression testing bit, taking snapshots and running code to compare them and report differences.
The approach is to take screen shots of the web page. We will have test case scripts written in CasperJs. During each test run it will take screen shots of the specified page. The screen shots are then compared with each other for any pixel differences. In case any difference is found its reported as failures. The test failures are reported as images marked with differences between the test runs.