Increase test coverage for vision

[djmgit]

Several modules and sections in Vision's source code presently does not contain any tests.
The aim of this issue is to add more tests in Vision.

Procedure:

• Run make test
• Note the modules for which it shows [no test files]
• Write tests for those modules, ensure the tests work as expected.
• Create a issue for the tests you have added mentioning the modules it covers, refer to this issue as the parent issue.
• Send a PR containing your changes.