Static vs Dynamic Testing

// ── STATIC ANALYSIS TOOLS (run without executing code) ────────
// ESLint catches code quality issues statically:
// Before: no-op reassignment would cause a bug
function calculateDiscount(price, percent) {
    let result = price;     // ESLint warning: 'result' is assigned but never used
    result = price - (price * percent);  // missing return
}

// ── MISSING RETURN - caught by static analysis before testing:
// TypeScript (static type checker) catches:
function getUser(id: number): User {
    if (id > 0) {
        return db.find(id);
    }
    // TypeScript error: Function lacks ending return statement
    // and return type does not include 'undefined'
}

// ── REQUIREMENTS REVIEW (static testing of specifications) ─────
// Spec: "User must be able to log in with email and password"
// Static review questions:
// ❓ What happens if email is not registered?
// ❓ How many failed attempts before lockout?
// ❓ Does the spec cover forgot password flow?
// ❓ What are the password strength requirements?
// These questions catch requirement defects BEFORE development.

// ── DYNAMIC TESTING (executing the code) ──────────────────────
test("login returns 401 for unregistered email", async () => {
    const res = await post("/login", { email: "unknown@test.com", password: "test" });
    expect(res.status).toBe(401);
});
// This dynamic test verifies behavior at runtime.