Running tests is typically performed by a build server rather than directly by Octopus Deploy. If you are already building your application in an external tool which pushes packages to Octopus, that may also be a good place to run the tests.
That said, t is certainly possible to run tests in Octopus. Are you already using a framework or tool for running integration tests? We have community-contributed steps for running the most popular unit tests frameworks, which are MSTest, NUnit and xUnit. Just search for the name of your test framework when selecting a step to add to your deployment process, and the contributed step should appear.
We don’t have any built-in or community contributed steps for running tests with SoapUI. However, if SoapUI can be configured to run your tests from the command line, you can do that within a script step.
Let me know how it goes, or if I can assist you further!