Sprint 99 — PM QA 5 Continuous Rounds: DifficultyBadge Platform-Aware Extension + Week Calculation Formula Fix + sourcePlatform Prop Propagation

Background

After Programmers integration (Sprint 95–98), a PM-led QA session surfaced multiple UI/logic bugs across 5 rounds of iterative testing. Each round identified new issues until round 5 achieved zero defects.

Goals

1. Fix DifficultyBadge to correctly render Programmers levels (Lv.1–5) vs BOJ tiers (Bronze–Ruby)
2. Fix week calculation formula returning incorrect week numbers
3. Fix sourcePlatform prop not propagating through all component layers
4. Achieve 0 defects in round 5 QA

QA Round Summary

Key Bug Fixes

DifficultyBadge Platform-Aware Extension

Problem: DifficultyBadge used BOJ tier strings ('BRONZE', 'SILVER', etc.) as the only display path. When sourcePlatform='PROGRAMMERS', the badge showed nothing or an error.

Fix:

// frontend/src/components/DifficultyBadge.tsx
interface DifficultyBadgeProps {
  difficulty: string;
  sourcePlatform: 'BOJ' | 'PROGRAMMERS';
}

export function DifficultyBadge({ difficulty, sourcePlatform }: DifficultyBadgeProps) {
  if (sourcePlatform === 'PROGRAMMERS') {
    const level = parseInt(difficulty.replace('LEVEL_', ''), 10);
    return <span className={`badge badge-programmers-lv${level}`}>Lv.{level}</span>;
  }
  // BOJ tier rendering (existing)
  return <span className={`badge badge-${difficulty.toLowerCase()}`}>{TIER_LABEL[difficulty]}</span>;
}

Week Calculation Formula Fix

Problem: Week number calculation was off by 1 for weeks starting on Monday. The formula used Math.ceil(dayOfMonth / 7) which doesn't account for the day-of-week offset.

Fix: Used ISO week number calculation aligned to the study's startDate:

function getStudyWeekNumber(date: Date, studyStartDate: Date): number {
  const diffMs = date.getTime() - studyStartDate.getTime();
  const diffDays = Math.floor(diffMs / (1000 * 60 * 60 * 24));
  return Math.floor(diffDays / 7) + 1;
}

sourcePlatform Prop Propagation

Problem: sourcePlatform was available in the page-level data fetch but wasn't being passed down through intermediate components to DifficultyBadge.

Fix: Traced the prop through 3 intermediate components:

1. ProblemListPage → ProblemTable (added sourcePlatform)
2. ProblemTable → ProblemRow (added sourcePlatform)
3. ProblemRow → DifficultyBadge (added sourcePlatform)

Added sourcePlatform to each component's props interface.

Verification

Decisions

• Platform-aware DifficultyBadge: Single component handles both platforms via sourcePlatform discriminant. No separate ProgrammersDifficultyBadge component.
• ISO-aligned week calculation: Study week number is relative to studyStartDate, not the calendar month. This aligns with how study coordinators communicate week numbers.
• Prop drilling accepted for now: 3-level prop drilling for sourcePlatform is acceptable. If more levels are added, context API or SWR key redesign is preferred.

Lessons Learned

• PM QA sessions surface integration gaps that unit tests miss: Unit tests verified each component in isolation, but the prop propagation gap was only visible end-to-end.
• Scouting agents can misidentify component responsibility: Sprint 99 SSOT incident — scout reported DifficultyBadge didn't need changes because the prop was "available", without tracing whether it actually reached the component.
• Prop propagation check list: When adding a new prop to a leaf component, trace it upward through every ancestor. Document the chain: Page → Table → Row → Badge.
• Iterative QA rounds converge: 5 rounds is acceptable for a feature this size. Define "done" as 0 defects in a full round, not a fixed number of rounds.