Add missing unit tests

[damithc]

Create one PR for each Test class.

• PR name can be Add unit tests for {ClassName} class e.g Add unit tests for Foo class
• Omit the Fixes #.... phrase from the PR.
• Test class name should match class being unit tested.
• Where dependency injection is too hard to use, the SUT need not be isolated from dependencies. i.e. Unit + integration tests