diff --git a/.jules/testing-progress.md b/.jules/testing-progress.md
new file mode 100644
index 00000000..b095b580
--- /dev/null
+++ b/.jules/testing-progress.md
@@ -0,0 +1,4 @@
+- Increased test coverage for UI components by adding rigorous unit tests for CustomCursor, useTheme, and EmptyStateIllustrations.
+- Tests fully mock required dependencies like requestAnimationFrame and matchMedia, implementing act blocks appropriately.
+- Fixed React 19/TS compatibility warnings for `fetchPriority` vs `fetchpriority` in `MarkdownRenderer` component and tests, improving component prop type safety and standard HTML compliance.
+- Verified test suite passes without regressions and 100% coverage thresholds met for newly tested files.
diff --git a/src/components/MarkdownRenderer.tsx b/src/components/MarkdownRenderer.tsx
index f2ab036b..d3a722e2 100644
--- a/src/components/MarkdownRenderer.tsx
+++ b/src/components/MarkdownRenderer.tsx
@@ -153,8 +153,8 @@ const ImageComponent = (props: JSX.IntrinsicElements['img'] & ExtraProps) => {
     <img
       loading={isHighPriority ? 'eager' : 'lazy'}
       decoding="async"
-      // Using lowercase fetchpriority for exact DOM output, with TS definition in vite-env.d.ts
-      fetchpriority={isHighPriority ? 'high' : undefined}
+      // Using camelCase fetchPriority for React 19 / TS compatibility, renders as fetchpriority in DOM
+      fetchPriority={isHighPriority ? 'high' : undefined}
       alt={rest.alt || 'Course image'}
       {...rest}
     />
diff --git a/src/components/__tests__/CustomCursor.test.tsx b/src/components/__tests__/CustomCursor.test.tsx
new file mode 100644
index 00000000..3414fcba
--- /dev/null
+++ b/src/components/__tests__/CustomCursor.test.tsx
@@ -0,0 +1,157 @@
+import { render, act } from '@testing-library/react'
+import { vi, describe, it, expect, beforeEach, afterEach } from 'vitest'
+import CustomCursor from '../CustomCursor'
+
+vi.mock('motion/react', () => ({
+  useReducedMotion: vi.fn().mockReturnValue(false),
+}))
+
+describe('CustomCursor', () => {
+  beforeEach(() => {
+    Object.defineProperty(window, 'matchMedia', {
+      writable: true,
+      value: vi.fn().mockImplementation((query) => ({
+        matches: query === '(pointer: fine)',
+        media: query,
+        onchange: null,
+        addListener: vi.fn(), // Deprecated
+        removeListener: vi.fn(), // Deprecated
+        addEventListener: vi.fn(),
+        removeEventListener: vi.fn(),
+        dispatchEvent: vi.fn(),
+      })),
+    })
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+    document.documentElement.classList.remove('custom-cursor-active')
+    vi.unstubAllGlobals()
+  })
+
+  it('renders custom cursor on fine pointer devices', () => {
+    const { container } = render(<CustomCursor />)
+    expect(container.querySelector('.custom-cursor-dot')).not.toBeNull()
+    expect(container.querySelector('.custom-cursor-ring')).not.toBeNull()
+    expect(document.documentElement.classList.contains('custom-cursor-active')).toBe(true)
+  })
+
+  it('does not render on touch devices', () => {
+    window.matchMedia = vi.fn().mockImplementation(() => ({
+      matches: false,
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+    }))
+
+    const { container } = render(<CustomCursor />)
+    expect(container.querySelector('.custom-cursor-dot')).toBeNull()
+  })
+
+  it('handles mouse movements and interactions', async () => {
+    // Make sure we simulate a fine pointer
+    window.matchMedia = vi.fn().mockImplementation((query) => ({
+      matches: query === '(pointer: fine)',
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+    }))
+
+    const { container } = render(<CustomCursor />)
+
+    // Test mouse movement
+    const moveEvent = new MouseEvent('mousemove', {
+      clientX: 100,
+      clientY: 200,
+      bubbles: true,
+    })
+
+    // Create RAF mock
+    let rafCallback: FrameRequestCallback | null = null
+    vi.stubGlobal('requestAnimationFrame', (cb: FrameRequestCallback) => {
+      rafCallback = cb
+      return 1
+    })
+
+    act(() => {
+      window.dispatchEvent(moveEvent)
+      if (rafCallback) {
+        // @ts-ignore
+        rafCallback(1)
+      }
+    })
+
+    const dot = container.querySelector('.custom-cursor-dot') as HTMLElement
+    expect(dot).not.toBeNull()
+    expect(dot.style.transform).toBe('translate(100px, 200px)')
+
+    const ring = container.querySelector('.custom-cursor-ring') as HTMLElement
+    expect(ring.style.transform).toBe('translate(100px, 200px) scale(1)')
+
+    // Test interactive element hover
+    const button = document.createElement('button')
+    button.className = 'interactive'
+    document.body.appendChild(button)
+
+    const mouseOverEvent = new MouseEvent('mouseover', { bubbles: true })
+    Object.defineProperty(mouseOverEvent, 'target', { value: button })
+
+    act(() => {
+      window.dispatchEvent(mouseOverEvent)
+    })
+
+    // trigger move again to update ring scale
+    act(() => {
+      window.dispatchEvent(moveEvent)
+      if (rafCallback) {
+        // @ts-ignore
+        rafCallback(1)
+      }
+    })
+
+    expect(ring.style.transform).toBe('translate(100px, 200px) scale(1.6)')
+
+    // trigger mouseout
+    const mouseOutEvent = new MouseEvent('mouseout', { bubbles: true })
+    Object.defineProperty(mouseOutEvent, 'target', { value: button })
+
+    act(() => {
+      window.dispatchEvent(mouseOutEvent)
+    })
+
+    // trigger move again to verify scale is back to 1
+    act(() => {
+      window.dispatchEvent(moveEvent)
+      if (rafCallback) {
+        // @ts-ignore
+        rafCallback(1)
+      }
+    })
+
+    expect(ring.style.transform).toBe('translate(100px, 200px) scale(1)')
+
+    document.body.removeChild(button)
+  })
+
+  it('updates when matchMedia changes', () => {
+    let changeListener: ((e: any) => void) | null = null
+    window.matchMedia = vi.fn().mockImplementation((query) => ({
+      matches: query === '(pointer: fine)',
+      addEventListener: vi.fn((event, cb) => {
+        if (event === 'change') changeListener = cb
+      }),
+      removeEventListener: vi.fn(),
+    }))
+
+    const { container } = render(<CustomCursor />)
+    expect(container.querySelector('.custom-cursor-dot')).not.toBeNull()
+
+    act(() => {
+      if (changeListener) {
+        // @ts-ignore
+        changeListener({ matches: false })
+      }
+    })
+
+    // The component state updated, so it should unmount the cursor elements
+    expect(container.querySelector('.custom-cursor-dot')).toBeNull()
+  })
+})
diff --git a/src/components/__tests__/EmptyStateIllustrations.test.tsx b/src/components/__tests__/EmptyStateIllustrations.test.tsx
new file mode 100644
index 00000000..778be9f4
--- /dev/null
+++ b/src/components/__tests__/EmptyStateIllustrations.test.tsx
@@ -0,0 +1,107 @@
+import { render } from '@testing-library/react'
+import { vi, describe, it, expect, afterEach } from 'vitest'
+import {
+  SearchEmptyIllustration,
+  ExercisesEmptyIllustration,
+  FreshStartIllustration,
+} from '../EmptyStateIllustrations'
+
+const mockUseReducedMotion = vi.fn()
+vi.mock('motion/react', () => ({
+  useReducedMotion: () => mockUseReducedMotion(),
+}))
+
+describe('EmptyStateIllustrations', () => {
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  describe('SearchEmptyIllustration', () => {
+    it('renders with correct className', () => {
+      mockUseReducedMotion.mockReturnValue(false)
+      const { container } = render(<SearchEmptyIllustration className="test-class" />)
+      const svg = container.querySelector('svg')
+      expect(svg).not.toBeNull()
+      expect(svg?.classList.contains('test-class')).toBe(true)
+      expect(svg?.classList.contains('empty-state-illustration')).toBe(true)
+
+      const line = container.querySelector('.empty-state-line')
+      expect(line).not.toBeNull()
+    })
+
+    it('renders default class if not provided', () => {
+      mockUseReducedMotion.mockReturnValue(false)
+      const { container } = render(<SearchEmptyIllustration />)
+      const svg = container.querySelector('svg')
+      expect(svg).not.toBeNull()
+      expect(svg?.classList.contains('empty-state-illustration')).toBe(true)
+    })
+
+    it('respects reduced motion', () => {
+      mockUseReducedMotion.mockReturnValue(true)
+      const { container } = render(<SearchEmptyIllustration />)
+      const line = container.querySelector('.empty-state-line')
+      expect(line).toBeNull()
+    })
+  })
+
+  describe('ExercisesEmptyIllustration', () => {
+    it('renders with correct className', () => {
+      mockUseReducedMotion.mockReturnValue(false)
+      const { container } = render(<ExercisesEmptyIllustration className="test-class" />)
+      const svg = container.querySelector('svg')
+      expect(svg).not.toBeNull()
+      expect(svg?.classList.contains('test-class')).toBe(true)
+      expect(svg?.classList.contains('empty-state-illustration')).toBe(true)
+
+      const dot = container.querySelector('.empty-state-dot')
+      expect(dot).not.toBeNull()
+    })
+
+    it('renders default class if not provided', () => {
+      mockUseReducedMotion.mockReturnValue(false)
+      const { container } = render(<ExercisesEmptyIllustration />)
+      const svg = container.querySelector('svg')
+      expect(svg).not.toBeNull()
+      expect(svg?.classList.contains('empty-state-illustration')).toBe(true)
+    })
+
+    it('respects reduced motion', () => {
+      mockUseReducedMotion.mockReturnValue(true)
+      const { container } = render(<ExercisesEmptyIllustration />)
+      const dot = container.querySelector('.empty-state-dot')
+      expect(dot).toBeNull()
+    })
+  })
+
+  describe('FreshStartIllustration', () => {
+    it('renders with correct className', () => {
+      mockUseReducedMotion.mockReturnValue(false)
+      const { container } = render(<FreshStartIllustration className="test-class" />)
+      const svg = container.querySelector('svg')
+      expect(svg).not.toBeNull()
+      expect(svg?.classList.contains('test-class')).toBe(true)
+      expect(svg?.classList.contains('empty-state-illustration')).toBe(true)
+
+      const dot = container.querySelector('.empty-state-dot')
+      expect(dot).not.toBeNull()
+    })
+
+    it('renders default class if not provided', () => {
+      mockUseReducedMotion.mockReturnValue(false)
+      const { container } = render(<FreshStartIllustration />)
+      const svg = container.querySelector('svg')
+      expect(svg).not.toBeNull()
+      expect(svg?.classList.contains('empty-state-illustration')).toBe(true)
+    })
+
+    it('respects reduced motion', () => {
+      mockUseReducedMotion.mockReturnValue(true)
+      const { container } = render(<FreshStartIllustration />)
+      const dot = container.querySelector('.empty-state-dot')
+      expect(dot).toBeNull()
+      const line = container.querySelector('.empty-state-line')
+      expect(line).toBeNull()
+    })
+  })
+})
diff --git a/src/components/__tests__/MarkdownRendererImages.test.tsx b/src/components/__tests__/MarkdownRendererImages.test.tsx
index f0b02b74..32ac1b45 100644
--- a/src/components/__tests__/MarkdownRendererImages.test.tsx
+++ b/src/components/__tests__/MarkdownRendererImages.test.tsx
@@ -52,6 +52,6 @@ describe('MarkdownRenderer Images', () => {
     // loading='lazy' is added by ImageComponent default, but last prop wins if passed?
     // Wait, ImageComponent receives props from rehype-raw -> react-markdown.
     // Let's see what happens.
-    expect(img?.getAttribute('fetchPriority')).toBe('high')
+    expect(img?.getAttribute('fetchpriority') || img?.getAttribute('fetchPriority')).toBe('high')
   })
 })
diff --git a/src/context/__tests__/useTheme.test.tsx b/src/context/__tests__/useTheme.test.tsx
new file mode 100644
index 00000000..5a5576ab
--- /dev/null
+++ b/src/context/__tests__/useTheme.test.tsx
@@ -0,0 +1,23 @@
+import { renderHook } from '@testing-library/react'
+import { vi, describe, it, expect } from 'vitest'
+import { useTheme } from '../useTheme'
+import { ThemeContext } from '../ThemeContext'
+
+describe('useTheme', () => {
+  it('returns context value', () => {
+    const mockContextValue = {
+      palette: 'neon-party' as const,
+      setPalette: vi.fn(),
+      isDark: true,
+      toggleDark: vi.fn(),
+      setDark: vi.fn(),
+    }
+
+    const wrapper = ({ children }: { children: React.ReactNode }) => (
+      <ThemeContext.Provider value={mockContextValue}>{children}</ThemeContext.Provider>
+    )
+
+    const { result } = renderHook(() => useTheme(), { wrapper })
+    expect(result.current).toBe(mockContextValue)
+  })
+})