Job-Ready Software Engineering / 03

APIs, HTTP, and debugging

35 minutes · Developers and QA professionals

Debugging starts with a question

Replace guesses with evidence

The request/response contract

Method and URL
Headers and body
Server behavior
Status and response body

Status codes are signals

2xx — success
3xx — redirect
4xx — request or permission problem
5xx — server failure

A reliable debugging loop

Reproduce
Record
Compare
Narrow
Form one hypothesis
Change one thing
Verify

Evidence to collect

Exact URL and method
Timestamp and environment
Safe request details
Status and response
Logs
Reproduction frequency

Demo: diagnose a broken endpoint

POST /api/applications — expected 201 — actual 500

Pause: write the bug report

Title
Steps to reproduce
Expected result
Actual result
Evidence
Suspected cause

Your artifact

Publish a sanitized bug report
Include an API collection
Explain the evidence

Next step

Make the artifact.

Publish your work, then continue to the next lesson.