The shift in nature of Web content from static documents to dynamic Rich Internet Applications (RIA) has not been accompanied by a similar shift in testing methodology. RIAs are software applications, and as such can benefit from the testing methodologies used in the field of software development. Because this shift in nature is fairly recent, traditional software testing methodology has not been given the importance it is due within the domain of accessibility. We will attempt to show the merits of Traditional Software Testing as applied to the domain of Web accessibility, and to make the case for a shift of focus from post hoc validation to proactive testing as the preferred means of assuring accessibility for Web sites and applications.