QA Project Case Studies

Last reviewed: — by Rammehar Dhiman, Senior QA Automation Engineer

Real-world testing scenarios, defect root-cause analyses, severity breakdowns, code fixes, and architectural decisions from 12+ years of enterprise Quality Assurance.

Rammehar Dhiman

Curated by Rammehar Dhiman

Senior QA Automation Engineer & Founder

These case studies document actual challenges, unexpected production-blocking defects, code refactoring patterns, and mitigation strategies from real enterprise systems across BFSI, E-Commerce, Healthcare, and Mobile platforms.

Case Study 1 • E-Commerce / Retail

Multi-Currency E-Commerce Checkout Module Testing

Duration6 Weeks
Team Size3 QA Engineers
Defect Density7% (14 / 200 TCs)
Primary FocusBoundary Values & Precision

Requirement & Context

A major retail client launched a multi-currency payment gateway integration supporting 12 currencies across Europe and Asia-Pacific. The core risk was currency conversion drift, rounding inaccuracies, and session timeouts during high-value transactions exceeding ,000 equivalent.

Key Defects Uncovered

Bug ID Description Severity Priority
BUG-441 EUR→INR amounts >10,000 show -1 paise rounding error on invoice subtotal Critical P1
BUG-442 GBP currency symbol displays as $ on PDF order confirmation receipt High P2
BUG-443 Payment gateway session timeout clears shopping cart silently without user alert High P1

Code Fix Recommendation

// FIX FOR BUG-441: Enforce BigDecimal with HALF_EVEN rounding mode
public BigDecimal convertCurrency(BigDecimal amount, BigDecimal exchangeRate) {
    return amount.multiply(exchangeRate).setScale(2, RoundingMode.HALF_EVEN);
}
Lessons Learned

Float precision issues are systemic in financial applications. Always enforce BigDecimal in backend monetary handling and write explicit boundary tests at currency conversion thresholds.

Case Study 2 • Banking / BFSI

Core Banking Loan Origination System (LOS) Testing

Duration8 Weeks
Target Users200,000+ Active Customers
Form States47 Conditional Workflows
IntegrationCIBIL Credit Rating API

The Release-Blocking Defect

During exploratory validation of self-employed applicant profiles earning >₹50 Lakhs annually, we identified BUG-2047. The interest calculation engine applied the annual interest rate variable inside a monthly loop, resulting in calculated Equated Monthly Installments (EMIs) appearing 12x higher than actual values.

CIBIL API Mock Code Assertion

// WireMock CIBIL API Response Stub for Loan Validation
stubFor(get(urlEqualTo("/cibil/v2/score?pan=ABCDE1234F"))
    .willReturn(aResponse()
        .withStatus(200)
        .withHeader("Content-Type", "application/json")
        .withBody("{\"cibilScore\": 785, \"tier\": \"PRIME\"}")));

Impact Prevention Summary

The release was halted 48 hours prior to deployment. The microservice calculation logic was patched, re-tested across 180 loan product permutations, and verified through automated API assertions before final executive sign-off.

Case Study 3 • Healthcare / Compliance

HIPAA-Compliant Patient Appointment Management System

Testing healthcare applications requires strict adherence to Personally Identifiable Information (PII) data privacy standards. During testing of an automated SMS notification microservice, we discovered BUG-788: cancellation SMS alerts were dispatched to the previous appointment's patient phone number due to variable scope reuse inside the notification worker loop.

Privacy & Compliance Impact

Sending medical appointment details to unverified recipients constitutes a major HIPAA violation. Our recommendation led to strict immutability checks on notification payload DTOs.

Case Study 4 • Mobile QA (iOS / Android)

Cross-Platform Mobile Food Delivery App Automation

Device Tested OS Version Observed Bug Severity
Samsung Galaxy A52 Android 11 GPS location permission prompt appears twice sequentially Medium
iPhone SE (2nd Gen) iOS 15.4 Order Confirmation CTA button obscured below virtual keyboard High
Xiaomi Redmi Note 11 Android 12 (MIUI) App crashes during checkout due to OEM background memory kill policy Critical
Case Study 5 • API & Security Testing

Travel Booking REST API Security & Performance Suite

Endpoint P95 Latency SLA Benchmark Status
GET /api/flights 340 ms < 500 ms PASS
POST /api/bookings 1,240 ms < 800 ms FAIL (Release Blocked)
Case Study 6 • Test Automation Architecture

Building an Enterprise Selenium POM Automation Framework

Metric Before Automation After Framework Deployment
Regression Suite Duration 3 Days (Manual) 45 Minutes (Parallel)
Production Defect Escape Rate 8% 1.2%

Case Study & QA Project FAQs

Why are real project case studies important in QA learning?

Textbook QA examples explain theory, but real case studies demonstrate how boundary values, exploratory testing, and API security assertions prevent real financial and HIPAA compliance failures in production.

How can I present these case studies in my resume or interview?

Use the metrics provided (e.g. 76% faster regression runs, 91% flakiness reduction) along with the STAR method (Situation, Task, Action, Result) to demonstrate business impact.