The Quality Mindset

Subject intro · Quality · Testing · Terminology · 7 Principles

→ next slide  |  ESC overview

Each lesson: theory + engagement + homework introduction

Course Overview

Key references: ISTQB Foundation · Agile Methodology · Clean Code by Robert C. Martin

Quality is Quality — Car or Code, Same Standard

Quality is quality. The standard is the same — whether it rolls on four wheels or runs on a server.

(Software) Quality

"Quality is conformance to requirements." — Philip Crosby

Quality is Relative — Same Code, Different Verdict

function divide(a, b) {
  return a / b;
}

divide(10, 2);  // → 5     ✓ correct
divide(10, 0);  // → Infinity  ✗ is this "quality"?

// Quality depends on the REQUIREMENT:
// "If b is 0, the function must throw Error('Division by zero')"

function divide(a, b) {
  if (b === 0) throw new Error('Division by zero');
  return a / b;
}

// Now it conforms → quality improved
// The code changed, the requirement didn't

Quality is not absolute — it's always measured against a specification

Why Test? Real-world Failures

Cost of Fixing Bugs — The Earlier the Better

Source: IBM Systems Sciences Institute / NIST studies

Where Do Bugs Come From?

Error → Defect → Failure

// ERROR: developer writes assignment instead of comparison (human typo)
function applyDiscount(total, isMember) {
  if (isMember = true) {     // ← ERROR: should be ===
    return total * 0.9;
  }
  return total;
}
// DEFECT: isMember is always overwritten to true
// FAILURE: every customer gets a discount — financial loss

Not all defects become failures — some hide until specific conditions occur

Verification vs Validation

You can perfectly test a perfectly wrong product. Both matter.

Key Testing Terminology

What is ISTQB?

🔗 istqb.org — free glossary, syllabi, and sample exams for all certification levels

7 Principles of Testing (ISTQB)

AI Tools Are Here — Use Them With Brains

The quality mindset you're building here is exactly how you use AI responsibly. Trust, but verify.