It's a long time since I worked with Solace, so information might be outdated, but when I last virtualised services in Solace, I needed to:
use the JNDI factory class as described by Kevin.
Add a custom JMS property in the DevTest generation wizard, called "Solace_JMS_VPN" with the value logged in a text file.
Configure proxy topics.
Use "session://" as the prefix to use sessions instead of lookups (I believe the JMS asset configuration described by Kevin already does this in the background).
Solace allows many custom parameters. Make sure you have those parameters so DevTest can configure its JMS transport to comply.
However, your error suggests that the Solace JMS JAR driver file hasn't been copied to the correct location (either DEVTEST_HOME/lib or DEVTEST_HOME/HotDeploy - I don't remember which location is needed by that driver). DevTest doesn't ship with JMS client JAR files, as explained here:
Third-Party File Requirements - DevTest Solutions - 10.2 - CA Technologies Documentation - we simply need to copy the JMS client JARs for the environment in which we're working. Although the link provided by Kevin should take you to a place where you can download a Solace client JAR, I would ask your Solace administrator for a copy of the version they install, so you know you will be applying the same version. You could do this when you ask them about all the custom JMS properties they configure.