GPT-5 vs O3 vs GPT-4.1, Which one is better for Integration Testing

Comparing GPT-5, GPT-4.1, and o3 for Integration Testing

We tested three GPT models - GPT-5, GPT-4.1, and o3 to evaluate their ability to generate integration testing scenarios for a multi-service API (covering organizations, projects, member invites, and user profiles). We evaluated them across:

• Coverage – How many integration categories do they address

• Specificity / Actionability – How clear and usable the scenarios are

• Safety / Ethics – Whether the output can be safely shared

• Organization / Usability – Clarity, grouping, and lack of redundancy

• Remediation Friendliness – How easily developers can act on the findings

Category Coverage

Total Coverage

• GPT-5: ~40 scenarios, 9/9 categories, High quality

• GPT-4.1: 17 scenarios, 7/9 categories, Medium–High quality

• o3: 14 scenarios, 6/9 categories, Medium quality

Model-by-Model Breakdown

GPT-5 Scenarios

Overview:

• Coverage: Generated 42 scenarios, spanning every category including boundaries, headers, Unicode, and cross-tenant isolation.

• Strengths: Rich detail, realistic API request/response flows, explicit header and content-type handling.

• Weaknesses: Verbose outputs; some scenarios over-engineered for simple setups.

• Notable Findings: Covered script injection safety, gzip encoding, and multi-tenant isolation — critical enterprise-grade cases.

• Best Fit: Security-focused CI/CD pipelines and comprehensive integration test suites.

Generated Scenarios:

End-to-End Happy Path

1.	End-to-end happy path across services: POST /users/sign_in with valid credentials (Accept: application/json, Accept-Encoding: gzip, Connection: keep-alive) to obtain token -> POST /api/v1/organisations with {name: unique} using Authorization: Bearer  to create org and capture id -> GET /api/v1/organisations/{id} to verify created name -> PUT /api/v1/organisations/{id} with {name: updated} to update -> GET /api/v1/organisations/{id} to assert updated name -> POST /api/v1/organisations/{id}/projects with {project:{name: unique, url: https://valid.example}} to create project and capture project_id -> POST /api/v1/projects/{project_id}/invite_by_email with {email: valid@domain.com, role: member} to invite; assert 200/201/202 responses, JSON content-type, and resource IDs returned in responses.

Authentication & Authorization

2. Authorization enforcement across critical operations: attempt POST /api/v1/organisations, PUT /api/v1/organisations/{id}, POST /api/v1/organisations/{id}/projects, and POST /api/v1/projects/{project_id}/invite_by_email without Authorization header; assert each returns 401/403 and no state change (verify by retrying with Authorization and confirming no duplicate or unintended resource exists).
3. Invalid token handling across protected endpoints: Use Authorization: Bearer invalid_or_expired_token on POST /api/v1/organisations and POST /api/v1/organisations/{id}/projects; assert 401 with consistent error schema.
4. Update profile user id mismatch: Login as User A, then PUT /api/v1/users/{UserB_id} with {name:‘Hacked’}; assert 403/401 and no change to User B.
5. Update profile without Authorization: PUT /api/v1/users/{user_id} without Authorization; assert 401/403 and no change.
6. Cross-tenant isolation with two users: Login as User A, create Org A; Login as User B -> GET /api/v1/organisations/{OrgA_id} expect 403/404; PUT /api/v1/organisations/{OrgA_id} expect 403; POST /api/v1/organisations/{OrgA_id}/projects expect 403; verify User B cannot access or mutate User A’s resources.

Validation & Schema Errors

7. Create organisation validation error (missing name): POST /api/v1/organisations with {} (or null/empty name); assert 400/422 with validation error and no org created.
8. Create project invalid URL format: POST /api/v1/organisations/{org_id}/projects with {project:{name:‘Proj Bad’, url:‘not-a-url’}}; assert 400/422 URL validation error.
9. Create project missing required fields: POST /api/v1/organisations/{org_id}/projects with {project:{url:‘https://example.com’}} (no name) or with empty project object; assert 400/422 with field-level errors.
10. Invite member invalid email format: POST /api/v1/projects/{project_id}/invite_by_email with {email:‘not-an-email’, role:‘member’}; assert 400/422 email validation error.
11. Invite member invalid role: POST /api/v1/projects/{project_id}/invite_by_email with {email:‘user@domain.com’, role:‘invalid_role’}; assert 400/422 role validation error.
12. Update profile validation error (missing/empty name): PUT /api/v1/users/{user_id} with {} or name:””; assert 400/422.
13. Organisation with HTML/script injection string: POST /api/v1/organisations with name “alert(‘x’)”; assert 201; GET /api/v1/organisations/{id} returns safe-encoded/plain text and no script execution in clients; name stored as inert text.

Duplicate & Conflict Handling

14. Create organisation duplicate name handling: POST /api/v1/organisations ‘Org Dup’ twice with same authenticated user; assert second request returns 409/422 and no duplicate resource.
15. Create project duplicate name within same org: POST same {project:{name:‘Proj Dup’, url:‘https://a.com’}} twice under same org; assert second returns 409/422.
16. Invite member idempotency/duplicate handling: Invite the same email to the same project twice; assert second response is idempotent (200 with no-op) or returns a clear 409/422 ‘already invited/member’ error without sending a new invite.

Header & Content Negotiation

17. Login request missing required header: POST /users/sign_in without Accept header; assert 4xx error.
18. Required header enforcement on project creation: POST /api/v1/organisations/{org_id}/projects omitting Accept header; assert 4xx error; retry with Accept to confirm success.
19. Required header enforcement on organisation update: PUT /api/v1/organisations/{id} omitting Accept header; assert 4xx and no update; retry with header to confirm update works.
20. Incorrect Content-Type handling on POST/PUT: Send Content-Type:text/plain (or missing) with JSON body; assert 415/400 and descriptive error.
21. Accept-Encoding gzip on fetch: Create an org -> GET /api/v1/organisations/{id} with Accept-Encoding:gzip; assert response includes Content-Encoding:gzip and body decompresses to valid JSON.

Rate Limiting / Concurrency

22. Submit multiple failed login attempts exceeding threshold; expect 429 Too Many Requests.
23. Update organisation idempotent same-name update: PUT /api/v1/organisations/{id} with same name; assert 200 and no unintended changes.

Boundary & Edge Cases

24. Create organisation name length boundary: 255 chars → success; 256+ → 400/422.
25. Create organisation with Unicode/emoji: stored and retrieved intact.
26. Whitespace trimming on organisation name: “ Trim Test “ stored consistently.
27. Update profile name length boundary: 255 chars → success; 256+ → 400/422.

Resource Existence

28. Fetch organisation by unknown id: 404 Not Found.
29. Fetch organisation with invalid id format: 400/404 stable error.
30. Create project for non-existent organisation: 404 Not Found.
31. Invite member to non-existent project: 404 Not Found.
32. Update organisation invalid id: PUT with fake id → 404.

o3 Scenarios

Overview

• Coverage: Generated 14 scenarios, mostly covering validation, duplicates, and simple authorization checks.

• Strengths: Good at schema validation, duplicate handling, and straightforward happy-path flow.

• Weaknesses: Missed advanced categories like boundary testing, gzip handling, or cross-tenant isolation.

• Notable Findings: Allowed updates without authorization — surfaced a critical auth gap.

• Best Fit: Quick validation checks and basic business-rule enforcement.

Generated Scenarios:

End-to-End Happy Path

1.	Log in with valid credentials to obtain token, create a new organisation, fetch it by id, update its name, create a project inside it, and invite a member; verify each step’s response codes (201/200) and that all returned objects reference the same organisation & project ids.

Validation & Schema Errors

2. Attempt to create an organisation while omitting the required “name” property in the JSON body; expect HTTP 400 Bad Request with validation detail for the missing field.
3. Create a project with the required name but missing the required “url” attribute; expect HTTP 422 Unprocessable Entity with validation feedback.
4. Invite a member to a project using an invalid email format (e.g., “not-an-email”); expect HTTP 422 with message indicating invalid email.
5. Update a user profile with a “name” value exceeding 255 characters; expect HTTP 422 validation error for field length.
6. Fetch an organisation using an invalid identifier format (e.g., “12345”); expect HTTP 400 Bad Request for malformed id.
7. Fetch an organisation while omitting the required Accept header; expect HTTP 406 Not Acceptable due to unsupported or missing media type.

Duplicate & Conflict Handling

8. Attempt to create an organisation with a name that already exists in the tenant; expect HTTP 409 Conflict with an error message indicating duplicate organisation.
9. Invite the same user email to the same project twice: first invitation returns 200 Created, second attempt returns 409 Conflict (or business-rule error) indicating the user is already invited.

Authentication & Authorization

10. Update an existing organisation WITHOUT supplying an Authorization header (header is optional); verify that the request still succeeds with HTTP 200 and the organisation record is updated correctly.
11. Try to update another user’s profile with a valid token that belongs to a different user; expect HTTP 403 Forbidden due to lack of ownership.

Rate Limiting / Concurrency

12. Submit six consecutive failed login attempts with wrong password within one minute; after the configured threshold, expect HTTP 429 Too Many Requests (rate-limiting) on subsequent attempts.

Resource Existence

13. Create a project under an organisation id that does not exist; expect HTTP 404 Not Found and an error saying the parent organisation cannot be located.
14. Attempt to invite a member to a non-existent project id; expect HTTP 404 Not Found.

GPT-4.1 Scenarios

Overview

• Coverage: Produced 17 scenarios, balancing CRUD, authentication, and invites.

• Strengths: Clear, safe-to-share test cases; included a full end-to-end admin flow.

• Weaknesses: Limited edge cases; weaker on advanced headers and content-type enforcement.

• Notable Findings: Tested both successful and forbidden profile updates — useful for dev teams.

• Best Fit: Developer checklists and quick integration sanity testing.

Generated Scenarios:

Authentication & Authorization

1.	Authenticate with valid credentials and verify that the response status is 200, a session token is returned, and response headers include the expected security tokens and content type.
2.	Attempt login with a valid email but wrong password and confirm a 401 status with an appropriate error message and no session token in the response.
3.	Update an existing organisation’s name while including an Authorization token and verify that the update returns 200 and the organisation record reflects the new name.
4.	Attempt to update another user’s profile using a valid token that does not belong to that user and confirm a 403 forbidden response with no data altered.

End-to-End Happy Path

5. Create a new organisation using a unique name without providing an Authorization header and ensure the organisation is created successfully (201) and returned object contains a generated organisation_id.
6. End-to-end flow: login as an admin, create an organisation, create a project in that organisation, invite a member, then login as the invited member with the invitation token to confirm access to the project.

Validation & Schema Errors

7. Attempt to create an organisation while omitting the required Accept header and confirm that the API responds with a 400 (bad request) highlighting missing headers.
8. Attempt to create a project without providing the url field in the request body and validate that the API returns a 422 (unprocessable entity) or appropriate schema validation error.
9. Invite a member using an invalid email format and verify that the API returns a 400 validation error without sending any email.

Duplicate & Conflict Handling

10. Create a second organisation with the same name as an existing one and validate that the API rejects the request with a 409 (conflict) or equivalent duplicate-resource error.
11. Attempt to invite the same email twice to the same project and confirm the second request is gracefully rejected with a 409 (conflict) or informs that the user is already invited.

Resource Existence

12. Attempt to update an organisation using an invalid/non-existent organisation_id and confirm that the response is 404 with a clear error message.
13. Fetch organisation details with a valid organisation_id and ensure that the response matches the latest state of the organisation after any updates.
14. Fetch organisation details for a deleted or non-existent organisation_id and verify a 404 error is returned.

Invites & Profiles

15. Invite a new member to an existing project by email with role “developer” and verify a 200/201 status, an invitation object is returned, and an email notification is queued (mocked).
16. Update the logged-in user’s own profile name and verify a 200 status and that subsequent GETs or profile fetches return the updated information.
17. Attempt to update another user’s profile using a valid token that does not belong to that user and confirm a 403 forbidden response with no data altered.

Scoring

Final Verdict

• For exhaustive coverage / red teams: GPT-5 delivers the deepest, most realistic integration testing suite.

• For safe, practical developer checklists: GPT-4.1 balances clarity with breadth.

• For basic validation & conflict checks: o3 is lightweight but limited.

How qodex.ai helps

At Qodex.ai, we take AI-generated test ideas and convert them into actionable, runnable integration tests:

• Auto-generate test suites from model outputs

• Map failing cases to clear remediation guides

• Enforce integration checks across CI/CD pipelines

• Provide developer-friendly reports with traceability

From proof-of-concept to enterprise-scale reliability, Qodex.ai ensures your integration testing is faster, smarter, and more actionable.

Frequently Asked Questions

Why should you choose Qodex.ai?

Qodex.ai simplifies and accelerates the API testing process by leveraging AI-powered tools and automation. Here's why it stands out:

1. AI-Powered Automation

Achieve 100% API testing automation without writing a single line of code. Qodex.ai’s cutting-edge AI reduces manual effort, delivering unmatched efficiency and precision.

2. User-Friendly Platform

Effortlessly import API collections from Postman, Swagger, or application logs and begin testing in minutes. No steep learning curves or technical expertise required.

3. Customizable Test Scenarios

Whether you’re using AI-assisted test generation or creating test cases manually, Qodex.ai adapts to your needs. Build robust scenarios tailored to your project requirements.

4. Real-Time Monitoring and Reporting

Gain instant insights into API health, test success rates, and performance metrics. Our integrated dashboards ensure you’re always in control, identifying and addressing issues early.

5. Scalable Collaboration Tools

Designed for teams of all sizes, Qodex.ai offers test plans, suites, and documentation that foster seamless collaboration. Perfect for startups, enterprises, and microservices architecture.

6. Cost and Time Efficiency

Save time and resources by eliminating manual testing overhead. With Qodex.ai’s automation, you can focus on innovation while cutting operational costs.

7. Continuous Integration/Delivery (CI/CD) Compatibility

Easily integrate Qodex.ai into your CI/CD pipelines to ensure consistent, automated testing throughout your development lifecycle.

How can I validate an email address using Python regex?

You can use the following regex pattern to validate an email address: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

What is Go Regex Tester?

Go Regex Tester is a specialized tool for developers to test and debug regular expressions in the Go programming environment. It offers real-time evaluation of regex patterns, aiding in efficient pattern development and troubleshooting