Blog

Notes on API testing, from the team building the AI test engineer that keeps tests current on every PR.

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End-to-End Testing Tools: Browser and API

End-to-end testing tools by layer: Playwright, Cypress and Selenium for the browser; Postman, REST Assured, Step CI and Stresseur for API flows.

Mustafa Bayramoglu

  • end-to-end-testing
  • tools
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Playwright API Testing vs a Recorded Flow

Playwright API testing means writing each request by hand. A recorded flow is generated from real use. See where each fits and where Playwright wins.

Mustafa Bayramoglu

  • end-to-end-testing
  • playwright
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Flaky Tests: Causes and Fixes Below the Browser

Flaky tests pass and fail with no code change. Learn the four usual causes, how to find them, and which checks to move from the browser to API flows.

Mustafa Bayramoglu

  • end-to-end-testing
  • flaky-tests
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API Testing Framework: How to Choose One

How to choose an API testing framework: match it to your team's language, check how it runs in CI, and count what it costs to keep the tests current.

Mustafa Bayramoglu

  • api-testing
  • frameworks
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API Smoke Tests on Every Pull Request

API smoke tests run on every pull request: pick the few flows that prove the API is alive, run only them in GitHub Actions, and fail the check on a bad step.

Mustafa Bayramoglu

  • api-testing
  • smoke-testing
  • ci
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How to Test an API: A Short Walkthrough

How to test an API in three moves: send one request and read the response, chain calls into a flow, then run the flow on every pull request.

Mustafa Bayramoglu

  • api-testing
  • how-to
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REST API Testing, Step by Step

REST API testing in six steps: send one request, check the status, headers and body, chain calls, test failures, then run it on every pull request.

Mustafa Bayramoglu

  • api-testing
  • rest-api
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API Automation Testing: What to Automate First

API automation testing works best when you start with login and the money paths, then widen. Here is the order, what to skip, and how to run it on every PR.

Mustafa Bayramoglu

  • api-testing
  • api-automation
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Smoke Test vs Integration Test: What Each Checks

Smoke test vs integration test: a smoke test checks the build works at all, an integration test checks connected parts work together. See when each runs.

Mustafa Bayramoglu

  • unit-vs-integration
  • smoke-testing
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Integration Testing Examples for a REST API

Four integration testing examples for a REST API, each from request to assertion: create and read back, login token, bad input, and access control.

Mustafa Bayramoglu

  • integration-testing
  • api-testing
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Regression Testing vs Unit Testing

Regression testing vs unit testing: one names why you run a test, the other what it covers. How they overlap and where unit tests fall short.

Mustafa Bayramoglu

  • unit-vs-integration
  • regression-testing
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Integration Testing vs End-to-End Testing

Integration testing vs end-to-end testing: what each one covers, how they differ in scope, speed and failure causes, and when to write which.

Mustafa Bayramoglu

  • integration-testing
  • end-to-end-testing
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What Is Integration Testing? An API Example

What is integration testing? It checks that connected parts of an app work together. See the definition, the kinds, and a worked API example.

Mustafa Bayramoglu

  • unit-testing
  • integration-testing
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Load Testing: A Practical Guide for APIs

Load testing sends simulated traffic at an API to find where it slows or fails. See the test types, ramping vs arrival rate, thresholds and abort rules.

Mustafa Bayramoglu

  • load-testing
  • api-load-testing
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Testing Pyramid: Where the API Layer Fits

The testing pyramid explained: what unit, integration and end-to-end tests each do best, where API tests sit, and how many of each to write.

Mustafa Bayramoglu

  • testing-pyramid
  • integration-testing
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End-to-End Testing: A Guide to Both Layers

What end-to-end testing means, how it differs from unit and integration tests, why E2E suites get slow and flaky, and what to run in the browser vs the API.

Mustafa Bayramoglu

  • end-to-end-testing
  • flaky-tests
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Every Unit Test Passed, and Nobody Could Log In

2,189 agent-written unit tests and one API flow test, run against 8 ordinary bugs. Unit tests caught 5, the flow caught 6. Each missed what the other caught.

Mustafa Bayramoglu

  • unit-testing
  • ci
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Two Slower PRs: What Caught Them

Two ordinary pull requests slowed login 8x and the product list 2x. Unit tests passed and your coding agent's review noticed. What a check adds.

Mustafa Bayramoglu

  • ci
  • code-review
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Unit Test vs Integration Test: What Each Catches

Unit tests vs integration tests: what each one proves, what it misses, and what 8 real bugs showed when we ran 2,189 unit tests and one API flow.

Mustafa Bayramoglu

  • unit-testing
  • integration-testing
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Catch Breaking API Changes in Pull Requests

Catch breaking API changes in a pull request: diff the OpenAPI spec against the base branch with oasdiff in GitHub Actions and block the merge.

Mustafa Bayramoglu

  • ci
  • contract-testing
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Best Contract Testing Tools for Microservices

The best API contract testing tool for microservices depends on your stack. Pact, Spring Cloud Contract, Schemathesis and Dredd compared by what each checks.

Mustafa Bayramoglu

  • contract-testing
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How to Test an API Without Writing Test Code

Test an API without writing code: save requests with assertions, record real traffic, or generate tests from a spec, then see how each holds up.

Mustafa Bayramoglu

  • api-testing
  • ai-test-generation
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How Many Virtual Users to Load Test an API

How many virtual users to load test an API: work out the number from peak concurrency, then ramp load until latency or errors break to find the limit.

Mustafa Bayramoglu

  • load-testing
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Run API Tests on Every PR with GitHub Actions

Run API tests on every pull request with GitHub Actions: the pull_request trigger, fork and secrets limits, required checks, and keeping the suite current.

Mustafa Bayramoglu

  • ci
  • api-testing
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Test Multi-Step API Flows With Auth Tokens

Capture an authentication token from a login step, reuse it in every later request in a multi-step API flow, and test that an expired token gets rejected too.

Mustafa Bayramoglu

  • api-testing
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Postman vs Step CI for API Testing in CI

Postman vs Step CI for running API tests in CI: interface, git-friendliness, protocol support and cost, and who each one suits.

Mustafa Bayramoglu

  • ci
  • comparison
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k6 vs Loadmill for API Load Testing

Comparing k6 vs Loadmill for API load testing: Loadmill has pivoted to mobile test agents, so here is what k6 actually offers and who it suits.

Mustafa Bayramoglu

  • comparison
  • load-testing
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AI-Generated vs Hand-Written API Tests

AI-generated API tests are faster and broader; hand-written tests still lead on business logic and edge cases. Here is the tradeoff and how to combine both.

Mustafa Bayramoglu

  • comparison
  • ai-test-generation
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Best API Load Testing Tools for a Small Team

The best API load testing tool for a small engineering team is the one that runs today: k6, Locust, Artillery and Postman compared, plus where JMeter fits.

Mustafa Bayramoglu

  • load-testing
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Best AI Tools for API Test Generation

Kusho AI, Postman Agent Mode, Loadmill, Katalon and more, compared by how each actually generates API tests: from a spec, from traffic, or from a flow.

Mustafa Bayramoglu

  • ai-test-generation
  • api-testing
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Turn an OpenAPI Spec into Contract Tests

The concrete steps for turning an OpenAPI spec into tests, where schema-driven testing ends and contract testing begins.

Mustafa Bayramoglu

  • contract-testing
  • ai-test-generation
  • api-testing
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What Is API Testing? A Practical Guide

API testing sends requests straight to an API and checks the response. What it is, the five types, multi-step flows, how to write tests and run them in CI.

Mustafa Bayramoglu

  • api-testing
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Alternatives to Hand-Writing Postman Collections

The alternative to writing Postman collections by hand is generating them: from a spec, from recorded traffic, or from a flow. Here is what each path costs.

Mustafa Bayramoglu

  • api-testing
  • ai-test-generation
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API Tests from Real Traffic: 4 Tools Compared

Keploy, Speedscale, WireMock and Hoverfly compared on the same criteria: where each one sits, what it installs, what it captures, and how it replays.

Mustafa Bayramoglu

  • traffic-replay
  • ai-test-generation
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How to Keep API Tests Current with the Code

API tests go stale because they are hand-authored copies of a moving target. Four mechanisms keep API tests from going stale when the API changes.

Mustafa Bayramoglu

  • api-testing
  • ai-test-generation
  • ci
Keploy vs Postman for AI-Generated API Tests

Keploy vs Postman for AI-Generated API Tests

Keploy vs Postman for AI-generated API tests, compared on input, output, mocking, CI and price, using only each vendor's own public documentation.

Mustafa Bayramoglu

  • comparison
  • ai-test-generation
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Load Test an API with Realistic Multi-Step Flows

Load test an API with realistic user flows instead of single endpoints: the virtual user arithmetic, the ramp that finds the ceiling, and how to read the run.

Mustafa Bayramoglu

  • load-testing