[12.x] Enhance ValidatorAfterRule Test Coverage and Scenarios

[roshandelpoor]

This PR enhances the test coverage for the ValidatorAfterRule functionality by introducing additional test scenarios and improving the overall test structure.

Changes

• Introduced setUp() method to reduce code duplication and improve test maintainability
• Added new test cases:
  • Single closure validation handling
  • Empty array validation scenarios
  • Multiple error handling from the same rule
  • Chained after call validations

Why

These additional tests help ensure:

• More robust validation behavior verification
• Better coverage of edge cases
• Improved documentation of expected behavior
• Easier maintenance and understanding of the validation rules