SoapUI 5.2.1
Java 1.7_80
Ubuntu 15.10 64bit
Maven 3.2.5
The exception from the maven plugin is:
[ERROR] Failed to execute goal com.smartbear.soapui:soapui-maven-plugin:5.2.1:test (manage-solutions) on project studio-manager-integration-test: Execution manage-solutions of goal com.smartbear.soapui:soapui-maven-plugin:5.2.1:test failed: A required class was missing while executing com.smartbear.soapui:soapui-maven-plugin:5.2.1:test: com/jgoodies/forms/layout/CellConstraints
I tracked this down to a code change made mid last year
https://github.com/SmartBear/soapui/commit/0a944701fd135b16c72b372c8d75a475da3feca7
Specifically the introduction of jgoodies classes into the SimpleContainsAssertion and SimpleNotContainsAssertion
I fixed it locally by including a dependency to com.jgoodies:forms:1.0.7 in the maven plugin definition.