Understanding the role of the community, ASF, and Enterprise Tomcat vendors
Yes, bothTomcat 5.5.x and 6.0.x are thoroughly tested by the ASF community. Community testing is both ad hoc, that is, community users testing the new versions on their existing applications, as well as via the Java Community Process Technology Compatibility Kit (TCK) for the corresponding Servlet and JSP specifications. You can find high level information on the TCK program at:
TCK is licensed by Sun for validation. While you could license the relevant TCK for your environment, we would not recommend it as these tests are thoroughly exercised by the community on multiple configurations before an Apache Tomcat release is finalized.
In addition to the testing provided by the community, enterprise tomcat vendors that provide professional support to Apache Tomcat apply their own Quality Assurance processes to any Apache release before it is released as a supported product. In the case of SpringSource, this testing provides extended functional coverage, on load/stress scenarios as well as across a broader range of supported configurations than is typically tested by the community at large.
You can be assured that the combination of community, ASF and vendor testing provides you with an enterprise class Tomcat. However, when upgrading to any new release, we strongly encourage Tomcat customers to use strong internal processes including acceptance tests for new releases of any infrastructure software.