1. Code-Level & Foundation Testing

These tests are typically automated and run continuously as developers write and commit code.

• Unit Testing: Tests individual components or functions of the code in isolation to ensure they return the expected output for a given input.
• Component Testing: Evaluates slightly larger blocks of code (like a specific UI widget or a standalone background worker) to ensure they function correctly before being wired into the rest of the app.
• Static Application Security Testing (SAST): Automated scans of the source code to find common vulnerabilities (like SQL injection or hardcoded secrets) before the software is even compiled.

2. Integration & API Testing

SaaS platforms rely heavily on interconnected microservices, databases, and third-party APIs.

• Integration Testing: Verifies that different modules or microservices within your application communicate and transfer data correctly.
• API Testing: Bypasses the user interface to test the application's backend directly. It ensures endpoints handle requests correctly, return the right data structures (like JSON), and enforce proper rate limits and authentication.
• Database Testing: Ensures data integrity, validates database schemas, and checks that CRUD (Create, Read, Update, Delete) operations execute efficiently without locking up tables.

3. System & End-to-End (E2E) Testing

These tests evaluate the application as a fully integrated whole, simulating real user behavior.

• System Testing: Validates that the completely integrated software meets the specified business requirements.
• End-to-End (E2E) Testing: Simulates complete user journeys (e.g., signing up, connecting a wallet or payment method, performing a core action, and logging out) across the entire stack, including the frontend, backend, and external integrations.
• Cross-Browser and Cross-Device Testing: Ensures the web app renders and functions consistently across Chrome, Firefox, Safari, and various mobile operating systems.

4. Non-Functional Testing (Crucial for SaaS)

This phase ensures the application can handle the realities of the live market.

• Performance & Load Testing: Pushes the system to see how it handles anticipated user volumes. It measures response times, server resource utilization, and database query speeds under load.
• Stress Testing: Pushes the application beyond its expected limits until it breaks, determining the system's failover mechanisms and how gracefully it recovers from a crash.
• Dynamic Application Security Testing (DAST) & Penetration Testing: Simulates active cyberattacks on the running application to find vulnerabilities in authentication, session management, and data exposure.
• Disaster Recovery & Failover Testing: Intentionally shuts down nodes or databases to ensure backup systems automatically take over without catastrophic data loss.

5. Pre-Launch & Market Readiness

The final checks involving human feedback and pre-production staging.

• Regression Testing: An automated suite run every time a change is made to ensure that new features haven't broken existing functionality.
• User Acceptance Testing (UAT): Internal stakeholders or a closed beta group test the software to confirm it solves the intended business problem and is intuitive to use.
• Compliance & Accessibility Testing: Verifies the app meets legal data standards (like GDPR or SOC2) and accessibility guidelines (WCAG) for users with disabilities.
• Smoke / Sanity Testing: A final, lightweight checklist run immediately after deploying to the staging or production environment to ensure the core infrastructure (login, database connection, main dashboard) is alive and routing traffic correctly.