Designing a test suite for a banking application involves creating comprehensive unit tests, integration tests, and end-to-end (E2E) tests to ensure functionality, reliability, and security.

Unit Tests:

• Scope: Test individual components like functions, methods, or classes.
• Tools: Use frameworks like JUnit (Java), NUnit (C#), or pytest (Python).
• Examples: Validate calculations for interest rates, balance updates, and input validations.

Integration Tests:

• Scope: Test interactions between integrated units/modules.
• Tools: Use frameworks like Spring Test (Java), pytest-django (Python), or MSTest (C#).
• Examples: Test database interactions for transactions, API calls between microservices, and integration with third-party services (e.g., credit checks).

End-to-End Tests:

• Scope: Test the complete application flow from the user interface to the backend.
• Tools: Use tools like Selenium, Cypress, or TestCafe.
• Examples: Simulate user actions like logging in, transferring funds, checking balances, and receiving notifications.

Test Suite Design:

1. Unit Tests: High coverage, focusing on critical logic and edge cases.
2. Integration Tests: Validate key interactions, especially with external systems.
3. E2E Tests: Cover critical user journeys, ensuring smooth operation and compliance.

Automation and CI/CD: Integrate tests into a Continuous Integration/Continuous Deployment (CI/CD) pipeline using Jenkins, GitLab CI, or GitHub Actions to run tests automatically on code changes, ensuring quick feedback and continuous quality assurance.