In software development, testing isn’t a one-size-fits-all process. It’s a layered, collaborative effort that spans the entire Software Development Life Cycle (SDLC). From the moment a developer writes a line of code to the final thumbs-up from a user, different types of testing ensure that software is reliable, functional, and aligned with business needs.
This guide walks you through the major types of software testing, who’s involved, and how each type fits into real-world development cycles—especially in Agile environments where business agility and fast feedback are key.
1. Business Acceptance Testing (BAT)
What it is:
Business Acceptance Testing focuses on whether the product fulfills the business requirements—not just technical specs, but what the business actually needs to operate and serve customers.
Who performs it:
Usually Business Analysts (BAs), domain experts, or a dedicated BAT team.
When it’s done:
Toward the end of the development process, often right before or in parallel with User Acceptance Testing.
Key goal:
Ensure that the features built are not only functioning but solving the right business problems.
Example:
Let’s say you’re building a banking app. The BAT team verifies whether the “Transfer Funds” function deducts the correct amount, credits the right account, sends alerts, and logs the activity—because the business can’t run without those checks working flawlessly.
2. User Acceptance Testing (UAT)
What it is:
UAT is the final confirmation from real users that the software works in everyday scenarios. It bridges the gap between business expectations and the user experience.
Who performs it:
Actual end-users, sometimes internal clients or stakeholders.
When it’s done:
Just before go-live, after system and BAT testing are complete.
Key goal:
Validate that the system is usable, complete, and ready for release.
Example:
A healthcare scheduling app undergoes UAT by doctors and patients. They test if appointment booking works smoothly, records are accurate, and messages are received. If it passes UAT, it’s usually good to go.
3. Quality Assurance (QA) Testing
What it is:
QA is an ongoing process of verifying software quality through structured testing—functional, non-functional, performance, and security.
Who performs it:
QA testers or software test engineers.
When it’s done:
Throughout the development cycle, often integrated into sprints in Agile teams.
Key goal:
Prevent defects and ensure the product meets standards across browsers, devices, and scenarios.
Example:
Your app crashes when uploading a photo over 5MB. The QA team finds and logs the bug. Developers fix it. QA retests and confirms it works. That’s proactive defect prevention in action.
4. Developer Testing (Unit & Integration)
What it is:
Testing done by developers themselves. It includes:
Unit Testing: Verifies individual components or functions.
Integration Testing: Ensures that components interact correctly.
Who performs it:
Developers (Dev team).
When it’s done:
During the coding phase—often automated and run frequently.
Key goal:
Catch bugs early and reduce defect leakage into QA.
Example:
A dev writing code for the “Add to Cart” feature tests that it correctly adds an item and updates the cart count. They also test that the cart syncs with the stock management system. That’s unit + integration testing at work.
5. Integration Testing
What it is:
Tests how different parts of the system work together—APIs, services, databases, etc.
Who performs it:
Developers or QA engineers.
When it’s done:
After unit testing, before or during system testing.
Key goal:
Ensure that systems “talk” to each other correctly and data flows as intended.
Example:
In a messaging app, user A sends a message from an iPhone. User B receives it on a desktop browser. Integration testing checks this seamless handoff, regardless of device or platform.
6. System Testing
What it is:
A complete, end-to-end test of the full application in a test environment that mimics production.
Who performs it:
QA team.
When it’s done:
After integration testing and before UAT.
Key goal:
Ensure that all components work together under real-world conditions.
Example:
An airline booking system goes through system testing to ensure users can search flights, reserve seats, make payments, and receive confirmation—all without errors or delays.
7. Acceptance Testing
What it is:
A final checkpoint to confirm that the product meets the agreed-upon criteria. Combines elements of UAT and BAT.
Who performs it:
Product Owners, Business Analysts, clients, or users.
When it’s done:
Before software is released into production.
Key goal:
Gain formal approval for release from stakeholders.
Example:
A POS system is reviewed by a retail chain’s operations manager. They run a few sales, test receipt printing, review reporting, and give the green light for deployment.
8. Black Box Testing
What it is:
Functional testing where the internal code isn’t visible to the tester. Focus is solely on inputs and expected outputs.
Who performs it:
QA testers, UAT participants.
When it’s done:
Throughout the testing phases.
Key goal:
Validate software behavior from a user’s perspective.
Example:
A tester tries entering wrong login credentials. The system denies access and shows an error message. The tester doesn’t care how the code handles it—only that it behaves correctly.
9. White Box Testing
What it is:
Also known as structural or glass-box testing, this type examines the actual codebase—logic, branches, and paths.
Who performs it:
Developers or QA engineers with coding knowledge.
When it’s done:
Primarily during development and integration.
Key goal:
Ensure that the code logic is sound and conditions are fully tested.
Example:
A tester inspects a “discount calculation” function in an e-commerce app, making sure it handles edge cases like 0% or 100% discounts properly and doesn’t break with negative values.
10. Regression Testing
What it is:
Retesting after changes (like bug fixes or new features) to make sure nothing else broke.
Who performs it:
QA testers or automation frameworks.
When it’s done:
After code changes, sprint releases, or hotfixes.
Key goal:
Confirm that new updates don’t unintentionally affect existing features.
Example:
You introduce a new payment option. QA reruns checkout tests to make sure all payment types (credit, gift cards, PayPal) still work. That’s regression testing.
11. Exploratory Testing
What it is:
Unscripted, creative testing where testers “explore” the system, simulating what users might do.
Who performs it:
Experienced testers or even developers.
When it’s done:
Any time, often after scripted testing is complete.
Key goal:
Discover issues missed by standard tests.
Example:
A tester randomly switches between tabs in a travel app, quickly books a ticket, then edits their profile mid-checkout. Unexpected crashes or layout bugs uncovered this way can be critical.
Putting It All Together: Collaboration Across Roles
Testing is a team effort. Each role plays a key part in ensuring quality software.
| Role | Contribution to Testing |
|---|---|
| Business Analysts (BAs) | Define business requirements and validate them through BAT. Act as a bridge between users and devs. |
| Product Owners (POs) | Prioritize features, define acceptance criteria, and often lead acceptance testing. |
| Developers | Write and test code (unit/integration), fix defects, support regression testing. |
| QA Testers | Execute structured and exploratory testing, track issues, and verify fixes. |
| End-users / Clients | Validate real-world use cases and give the final approval during UAT. |
Example: Mobile Banking App
Let’s apply these testing types to a mobile banking app project:
BAT ensures that fund transfers, payments, and account overviews match business rules.
Developer testing checks each function (e.g., login, balance check) works independently.
Integration testing validates communication between modules like login, dashboard, and transaction APIs.
System testing checks the full workflow from login to logout under test conditions.
QA tests across devices and OS versions to catch performance or display issues.
UAT puts the app in front of bank staff and customers to simulate daily tasks.
Black box testing confirms behavior like form validations and error messages.
White box testing ensures the backend logic and conditions are handled correctly.
Regression testing reruns previous scenarios after a new “Quick Pay” feature is added.
Exploratory testing uncovers edge cases like changing settings mid-transfer or rotating the screen quickly.
Types of Testing
| Type of Testing | Description | Who Does It | When | Purpose |
|---|---|---|---|---|
| Business Acceptance (BAT) | Validates business rules and needs | BAs, BAT teams | Before UAT | Business alignment |
| User Acceptance (UAT) | Confirms real-world usability | End-users, clients | Final stage before launch | User validation |
| Quality Assurance (QA) | Formal testing across use cases and platforms | QA Testers | Throughout development | Find and fix defects |
| Developer Testing | Unit and integration tests at code level | Developers | During development | Code accuracy |
| Integration Testing | Tests data flow between modules | Devs, QA | After unit testing | Ensure module compatibility |
| System Testing | Validates the entire application | QA | Before UAT | Full system validation |
| Acceptance Testing | Combines BAT & UAT to approve for release | POs, BAs, users | Final review | Final approval |
| Black Box Testing | Tests software externally without code knowledge | QA, UAT testers | Throughout SDLC | Input/output validation |
| White Box Testing | Inspects code logic and paths | Developers, QA engineers | During development & integration | Code logic validation |
| Regression Testing | Verifies new changes don’t break existing features | QA | After updates | Stability assurance |
| Exploratory Testing | Informal, creative testing to uncover edge cases | QA, experienced devs | Any time | Discover hidden issues |
Effective testing is not just about checking boxes—it’s about building confidence. When testing types are clearly understood and roles are aligned, teams can deliver better software faster. In today’s Agile, fast-moving environments, a well-coordinated testing strategy turns quality from an afterthought into a team-wide commitment.
Encourage your teams to collaborate across testing types and use feedback loops to continuously improve. The stronger the testing culture, the more successful your releases will be.