Added Unit test for onDeckSelected

[Haz3-jolt]

Purpose / Description

Added Unit test to function with @NeedsTest.

Fixes

• Created test for onDeckSelected to address "15448: double-selecting deck does nothing".

Approach

• Unit test completed.

How Has This Been Tested?

• Ran the Unit test multiple times, and ensured it is passing.

Checklist

• [x] You have a descriptive commit message with a short title (first line, max 50 chars).
• [x] You have commented your code, particularly in hard-to-understand areas
• [x] You have performed a self-review of your own code
• [x] UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• [x] UI Changes: You have tested your change using the Google Accessibility Scanner