🚧Refactor unit test assertions

[kselena]

Complete The Item Below

• I have updated the title without removing the 🚧 emoji.

Description

Refactor all of the unit test assertions to use the FluentAssertions library.

This will greatly cleanup the unit testing side of things and make the creation of unit tests easier.

Acceptance Criteria

• Latest version of FluentAssertions Nuget package added to the project
• Refactor the files below:
  • GitHubActionIntegrationTests.cs - 209 lines
  • InvalidActionInputTests.cs - 52 lines
  • InvalidBranchExceptionTests.cs - 52 lines
  • InvalidSyntaxExpressionTests.cs - 52 lines
  • LoadEmbeddedResourceExceptionTests.cs - 48 lines

ToDo Items

• Change type labels added to this issue. Refer to the Change Type Labels section below.
• Priority label added to this issue. Refer to the Priority Type Labels section below.
• Issue linked to the correct project (if required).
• Issue linked to the correct milestone (if required).

Issue Dependencies

No response

Related Work

No response

Additional Information:

Change Type Labels

Change Type	Label
Bug Fixes	🐛bug
Breaking Changes	🧨breaking changes
New Feature	✨new feature
Workflow Changes	workflow
Code Doc Changes	🗒️documentation/code
Product Doc Changes	📝documentation/product

Priority Type Labels

Priority Type	Label
Low Priority	low priority
Medium Priority	medium priority
High Priority	high priority

Code of Conduct

• I agree to follow this project's Code of Conduct.