Unit tests assume Docker installed

[DavidBrainard]

Would be better to check for Docker and skip the test, rather than indicating an actual failure, if Docker is not installed. This is something to do on a very rainy day when someone is very bored.

[githubkusi]

currently, you don't get a failure, you correctly handled this in TbDockerTest>checkIfServerPresent with testCase.assumeTrue(dockerExist...). This test doesn't show up as error. All fine even for people without docker