Issue 13 | Phase D: Browser Integration Testing and Accessibility (a11y) Acceptance

运行测试：

node test.js
# ✅ 48/48 PASS

13.1 DOM Integration Tests (test-dom.js)

class DOMTestRunner {
  // Runs in a browser environment
  // Test button clicks → display updates
  // Test keyboard events → correct mapping
  // Test mode switching → CSS variable toggling + localStorage
}

13.1.1 Accessibility Tests (test-a11y.js)

class A11yTestRunner {
  // Verify all buttons have aria-label
  // Verify aria-live exists
  // Verify focus indicators
  // Verify Tab navigation order
  // Verify history accessibility
}

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13.2 Final Deliverables

13.2.1 Code File List

File	Lines	Creator	Description
index.html	65	ui-dev	Semantic HTML, ARIA tags
style.css	287	ui-dev	CSS variables dual theme, responsive
app.js	468	logic-dev	Shunting-yard engine + DOM binding
test-runner.js	200	logic-dev	Lightweight test framework
test.js	679	qa-engineer	48 unit tests
test-dom.js	550	qa-engineer	DOM integration tests
test-a11y.js	485	qa-engineer	Accessibility tests
test-runner.html	730	qa-engineer	Browser test page

13.2.2 Test Results

Test Level	Test Cases	Result
Unit Tests (Node.js)	48	✅ PASS
DOM Integration Tests (Browser)	20+	✅ PASS
Accessibility Tests (Browser)	15+	✅ PASS

13.2.3 Running in Browser

# Method 1: Open directly
open index.html

# Method 2: Local server
python3 -m http.server 8080
# Browser access http://localhost:8080

# Run test page
open test-runner.html

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