test(08-01): add failing tests for Calculator widget and registry constraints (RED)

- calculator-widget.test.tsx: 5 behaviour tests (render, arithmetic, div/0, keyboard, decimal)
- widget-registry.test.tsx: DASH-11 structure check for all 8 widget types including new Phase-8 types
- Both suites fail (RED baseline) — implementation does not exist yet

apps/web/src/components/dashboard/widget-registry.test.tsx

@@ -0,0 +1,55 @@
+import { describe, expect, it } from 'vitest';
+import { WIDGET_CONSTRAINTS, type WidgetType } from './widget-registry';
+
+/**
+ * DASH-11: Every WidgetType entry in WIDGET_CONSTRAINTS must have
+ * the four numeric grid-constraint fields: minW, minH, defaultW, defaultH.
+ */
+
+const ALL_WIDGET_TYPES: WidgetType[] = [
+  // Existing types
+  'clock',
+  'search',
+  'calendar',
+  'note',
+  // New types (Phase 8)
+  'calculator',
+  'favorites',
+  'link',
+  'stopwatch',
+];
+
+describe('WIDGET_CONSTRAINTS (DASH-11)', () => {
+  it('contains entries for all expected widget types', () => {
+    for (const type of ALL_WIDGET_TYPES) {
+      expect(
+        WIDGET_CONSTRAINTS,
+        `WIDGET_CONSTRAINTS must contain key "${type}"`,
+      ).toHaveProperty(type);
+    }
+  });
+
+  it.each(ALL_WIDGET_TYPES)(
+    'WIDGET_CONSTRAINTS["%s"] has numeric minW, minH, defaultW, defaultH',
+    (type) => {
+      const constraints = WIDGET_CONSTRAINTS[type];
+
+      expect(typeof constraints.minW, `${type}.minW must be a number`).toBe('number');
+      expect(typeof constraints.minH, `${type}.minH must be a number`).toBe('number');
+      expect(typeof constraints.defaultW, `${type}.defaultW must be a number`).toBe('number');
+      expect(typeof constraints.defaultH, `${type}.defaultH must be a number`).toBe('number');
+
+      expect(constraints.minW, `${type}.minW must be >= 1`).toBeGreaterThanOrEqual(1);
+      expect(constraints.minH, `${type}.minH must be >= 1`).toBeGreaterThanOrEqual(1);
+      expect(constraints.defaultW, `${type}.defaultW >= minW`).toBeGreaterThanOrEqual(constraints.minW);
+      expect(constraints.defaultH, `${type}.defaultH >= minH`).toBeGreaterThanOrEqual(constraints.minH);
+    },
+  );
+
+  it('WIDGET_CONSTRAINTS contains new Phase-8 keys', () => {
+    expect(Object.keys(WIDGET_CONSTRAINTS)).toContain('calculator');
+    expect(Object.keys(WIDGET_CONSTRAINTS)).toContain('favorites');
+    expect(Object.keys(WIDGET_CONSTRAINTS)).toContain('link');
+    expect(Object.keys(WIDGET_CONSTRAINTS)).toContain('stopwatch');
+  });
+});

apps/web/src/components/dashboard/widgets/calculator-widget.test.tsx

@@ -0,0 +1,85 @@
+import { render, screen, fireEvent } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+
+// Mock next-intl — returns the key so tests are locale-agnostic
+vi.mock('next-intl', () => ({
+  useTranslations: () => (key: string) => key,
+}));
+
+// Must import after mocks
+import { CalculatorWidget } from './calculator-widget';
+
+const defaultProps = {
+  instanceId: 'calc-1',
+  config: {},
+  isEditMode: false,
+};
+
+describe('CalculatorWidget', () => {
+  it('renders with initial display "0"', () => {
+    render(<CalculatorWidget {...defaultProps} />);
+    const display = screen.getByLabelText('Anzeige');
+    expect(display).toHaveTextContent('0');
+  });
+
+  it('calculates 7 + 3 = 10', () => {
+    render(<CalculatorWidget {...defaultProps} />);
+
+    fireEvent.click(screen.getByRole('button', { name: '7' }));
+    fireEvent.click(screen.getByRole('button', { name: '+' }));
+    fireEvent.click(screen.getByRole('button', { name: '3' }));
+    fireEvent.click(screen.getByRole('button', { name: /gleich/i }));
+
+    expect(screen.getByLabelText('Anzeige')).toHaveTextContent('10');
+  });
+
+  it('calculates 8 × 2 = 16', () => {
+    render(<CalculatorWidget {...defaultProps} />);
+
+    fireEvent.click(screen.getByRole('button', { name: '8' }));
+    fireEvent.click(screen.getByRole('button', { name: '×' }));
+    fireEvent.click(screen.getByRole('button', { name: '2' }));
+    fireEvent.click(screen.getByRole('button', { name: /gleich/i }));
+
+    expect(screen.getByLabelText('Anzeige')).toHaveTextContent('16');
+  });
+
+  it('shows "Fehler" on division by zero', () => {
+    render(<CalculatorWidget {...defaultProps} />);
+
+    fireEvent.click(screen.getByRole('button', { name: '5' }));
+    fireEvent.click(screen.getByRole('button', { name: '÷' }));
+    fireEvent.click(screen.getByRole('button', { name: '0' }));
+    fireEvent.click(screen.getByRole('button', { name: /gleich/i }));
+
+    expect(screen.getByLabelText('Anzeige')).toHaveTextContent('Fehler');
+  });
+
+  it('handles keyboard input: 5 * 6 Enter = 30', () => {
+    render(<CalculatorWidget {...defaultProps} />);
+
+    const container = screen.getByRole('application');
+
+    fireEvent.keyDown(container, { key: '5' });
+    fireEvent.keyDown(container, { key: '*' });
+    fireEvent.keyDown(container, { key: '6' });
+    fireEvent.keyDown(container, { key: 'Enter' });
+
+    expect(screen.getByLabelText('Anzeige')).toHaveTextContent('30');
+  });
+
+  it('handles decimal comma: 1,5 + 1,5 = 3', () => {
+    render(<CalculatorWidget {...defaultProps} />);
+
+    fireEvent.click(screen.getByRole('button', { name: '1' }));
+    fireEvent.click(screen.getByRole('button', { name: ',' }));
+    fireEvent.click(screen.getByRole('button', { name: '5' }));
+    fireEvent.click(screen.getByRole('button', { name: '+' }));
+    fireEvent.click(screen.getByRole('button', { name: '1' }));
+    fireEvent.click(screen.getByRole('button', { name: ',' }));
+    fireEvent.click(screen.getByRole('button', { name: '5' }));
+    fireEvent.click(screen.getByRole('button', { name: /gleich/i }));
+
+    expect(screen.getByLabelText('Anzeige')).toHaveTextContent('3');
+  });
+});