diff --git a/web-app/src/__tests__/i18n.test.ts b/web-app/src/__tests__/i18n.test.ts
new file mode 100644
index 000000000..644bc019d
--- /dev/null
+++ b/web-app/src/__tests__/i18n.test.ts
@@ -0,0 +1,52 @@
+import { describe, it, expect, vi } from 'vitest'
+
+// Mock the dependencies
+vi.mock('@/i18n/setup', () => ({
+  default: { t: vi.fn(), init: vi.fn() },
+}))
+
+vi.mock('@/i18n/react-i18next-compat', () => ({
+  useTranslation: vi.fn(() => ({ t: vi.fn() })),
+}))
+
+vi.mock('@/i18n/hooks', () => ({
+  useAppTranslation: vi.fn(() => ({ t: vi.fn() })),
+}))
+
+vi.mock('@/i18n/TranslationContext', () => ({
+  TranslationProvider: vi.fn(({ children }) => children),
+}))
+
+describe('i18n module', () => {
+  it('should re-export default from i18n/setup', async () => {
+    const i18nModule = await import('../i18n')
+    expect(i18nModule.default).toBeDefined()
+  })
+
+  it('should re-export useTranslation', async () => {
+    const i18nModule = await import('../i18n')
+    expect(i18nModule.useTranslation).toBeDefined()
+    expect(typeof i18nModule.useTranslation).toBe('function')
+  })
+
+  it('should re-export useAppTranslation', async () => {
+    const i18nModule = await import('../i18n')
+    expect(i18nModule.useAppTranslation).toBeDefined()
+    expect(typeof i18nModule.useAppTranslation).toBe('function')
+  })
+
+  it('should re-export TranslationProvider', async () => {
+    const i18nModule = await import('../i18n')
+    expect(i18nModule.TranslationProvider).toBeDefined()
+    expect(typeof i18nModule.TranslationProvider).toBe('function')
+  })
+
+  it('should export all expected functions', async () => {
+    const i18nModule = await import('../i18n')
+    const expectedExports = ['default', 'useTranslation', 'useAppTranslation', 'TranslationProvider']
+    
+    expectedExports.forEach(exportName => {
+      expect(i18nModule[exportName]).toBeDefined()
+    })
+  })
+})
\ No newline at end of file
diff --git a/web-app/src/components/ui/__tests__/hover-card.test.tsx b/web-app/src/components/ui/__tests__/hover-card.test.tsx
new file mode 100644
index 000000000..71e78cb7f
--- /dev/null
+++ b/web-app/src/components/ui/__tests__/hover-card.test.tsx
@@ -0,0 +1,168 @@
+import { describe, it, expect, vi } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import { HoverCard, HoverCardTrigger, HoverCardContent } from '../hover-card'
+
+// Mock Radix UI
+vi.mock('@radix-ui/react-hover-card', () => ({
+  Root: ({ children, ...props }: any) => <div data-testid="hover-card-root" {...props}>{children}</div>,
+  Trigger: ({ children, ...props }: any) => <button data-testid="hover-card-trigger" {...props}>{children}</button>,
+  Portal: ({ children, ...props }: any) => <div data-testid="hover-card-portal" {...props}>{children}</div>,
+  Content: ({ children, className, align, sideOffset, ...props }: any) => (
+    <div 
+      data-testid="hover-card-content" 
+      className={className}
+      data-align={align}
+      data-side-offset={sideOffset}
+      {...props}
+    >
+      {children}
+    </div>
+  ),
+}))
+
+describe('HoverCard Components', () => {
+  describe('HoverCard', () => {
+    it('should render HoverCard root component', () => {
+      render(
+        <HoverCard>
+          <div>Test content</div>
+        </HoverCard>
+      )
+
+      const hoverCard = screen.getByTestId('hover-card-root')
+      expect(hoverCard).toBeDefined()
+      expect(hoverCard).toHaveAttribute('data-slot', 'hover-card')
+      expect(screen.getByText('Test content')).toBeDefined()
+    })
+
+    it('should pass through props to root component', () => {
+      render(
+        <HoverCard openDelay={500}>
+          <div>Test content</div>
+        </HoverCard>
+      )
+
+      const hoverCard = screen.getByTestId('hover-card-root')
+      expect(hoverCard).toHaveAttribute('openDelay', '500')
+    })
+  })
+
+  describe('HoverCardTrigger', () => {
+    it('should render trigger component', () => {
+      render(
+        <HoverCardTrigger>
+          <span>Hover me</span>
+        </HoverCardTrigger>
+      )
+
+      const trigger = screen.getByTestId('hover-card-trigger')
+      expect(trigger).toBeDefined()
+      expect(trigger).toHaveAttribute('data-slot', 'hover-card-trigger')
+      expect(screen.getByText('Hover me')).toBeDefined()
+    })
+
+    it('should pass through props to trigger component', () => {
+      render(
+        <HoverCardTrigger disabled>
+          <span>Disabled trigger</span>
+        </HoverCardTrigger>
+      )
+
+      const trigger = screen.getByTestId('hover-card-trigger')
+      expect(trigger).toHaveAttribute('disabled')
+    })
+  })
+
+  describe('HoverCardContent', () => {
+    it('should render content with default props', () => {
+      render(
+        <HoverCardContent>
+          <div>Content here</div>
+        </HoverCardContent>
+      )
+
+      const portal = screen.getByTestId('hover-card-portal')
+      expect(portal).toHaveAttribute('data-slot', 'hover-card-portal')
+
+      const content = screen.getByTestId('hover-card-content')
+      expect(content).toBeDefined()
+      expect(content).toHaveAttribute('data-slot', 'hover-card-content')
+      expect(content).toHaveAttribute('data-align', 'center')
+      expect(content).toHaveAttribute('data-side-offset', '4')
+      expect(screen.getByText('Content here')).toBeDefined()
+    })
+
+    it('should render content with custom props', () => {
+      render(
+        <HoverCardContent align="start" sideOffset={8} className="custom-class">
+          <div>Custom content</div>
+        </HoverCardContent>
+      )
+
+      const content = screen.getByTestId('hover-card-content')
+      expect(content).toHaveAttribute('data-align', 'start')
+      expect(content).toHaveAttribute('data-side-offset', '8')
+      expect(content.className).toContain('custom-class')
+    })
+
+    it('should apply default styling classes', () => {
+      render(
+        <HoverCardContent>
+          <div>Content</div>
+        </HoverCardContent>
+      )
+
+      const content = screen.getByTestId('hover-card-content')
+      expect(content.className).toContain('bg-main-view')
+      expect(content.className).toContain('text-main-view-fg/70')
+      expect(content.className).toContain('rounded-md')
+      expect(content.className).toContain('border')
+      expect(content.className).toContain('shadow-md')
+    })
+
+    it('should merge custom className with default classes', () => {
+      render(
+        <HoverCardContent className="my-custom-class">
+          <div>Content</div>
+        </HoverCardContent>
+      )
+
+      const content = screen.getByTestId('hover-card-content')
+      expect(content.className).toContain('bg-main-view')
+      expect(content.className).toContain('my-custom-class')
+    })
+
+    it('should pass through additional props', () => {
+      render(
+        <HoverCardContent data-testprop="test-value">
+          <div>Content</div>
+        </HoverCardContent>
+      )
+
+      const content = screen.getByTestId('hover-card-content')
+      expect(content).toHaveAttribute('data-testprop', 'test-value')
+    })
+  })
+
+  describe('Integration', () => {
+    it('should render complete hover card structure', () => {
+      render(
+        <HoverCard>
+          <HoverCardTrigger>
+            <button>Trigger</button>
+          </HoverCardTrigger>
+          <HoverCardContent>
+            <div>Hover content</div>
+          </HoverCardContent>
+        </HoverCard>
+      )
+
+      expect(screen.getByTestId('hover-card-root')).toBeDefined()
+      expect(screen.getByTestId('hover-card-trigger')).toBeDefined()
+      expect(screen.getByTestId('hover-card-portal')).toBeDefined()
+      expect(screen.getByTestId('hover-card-content')).toBeDefined()
+      expect(screen.getByText('Trigger')).toBeDefined()
+      expect(screen.getByText('Hover content')).toBeDefined()
+    })
+  })
+})
\ No newline at end of file
diff --git a/web-app/src/components/ui/__tests__/sonner.test.tsx b/web-app/src/components/ui/__tests__/sonner.test.tsx
new file mode 100644
index 000000000..72aca5526
--- /dev/null
+++ b/web-app/src/components/ui/__tests__/sonner.test.tsx
@@ -0,0 +1,93 @@
+import { describe, it, expect, vi } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import { Toaster } from '../sonner'
+
+// Mock sonner
+vi.mock('sonner', () => ({
+  Toaster: ({ className, expand, richColors, closeButton, ...props }: any) => (
+    <div 
+      data-testid="toaster" 
+      className={className} 
+      {...props}
+      {...(expand !== undefined && { 'data-expand': expand })}
+      {...(richColors !== undefined && { 'data-rich-colors': richColors })}
+      {...(closeButton !== undefined && { 'data-close-button': closeButton })}
+    >
+      Toaster Component
+    </div>
+  ),
+}))
+
+describe('Toaster Component', () => {
+  it('should render toaster component', () => {
+    render(<Toaster />)
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toBeDefined()
+    expect(screen.getByText('Toaster Component')).toBeDefined()
+  })
+
+  it('should apply default className', () => {
+    render(<Toaster />)
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toHaveClass('toaster', 'group')
+  })
+
+  it('should pass through additional props', () => {
+    render(<Toaster position="top-right" duration={5000} />)
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toHaveAttribute('position', 'top-right')
+    expect(toaster).toHaveAttribute('duration', '5000')
+  })
+
+  it('should maintain default className with additional props', () => {
+    render(<Toaster position="bottom-left" />)
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toHaveClass('toaster', 'group')
+    expect(toaster).toHaveAttribute('position', 'bottom-left')
+  })
+
+  it('should handle custom expand prop', () => {
+    render(<Toaster expand />)
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toHaveAttribute('data-expand', 'true')
+  })
+
+  it('should handle custom richColors prop', () => {
+    render(<Toaster richColors />)
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toHaveAttribute('data-rich-colors', 'true')
+  })
+
+  it('should handle custom closeButton prop', () => {
+    render(<Toaster closeButton />)
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toHaveAttribute('data-close-button', 'true')
+  })
+
+  it('should handle multiple props', () => {
+    render(
+      <Toaster 
+        position="top-center" 
+        duration={3000} 
+        expand 
+        richColors 
+        closeButton 
+      />
+    )
+    
+    const toaster = screen.getByTestId('toaster')
+    expect(toaster).toHaveClass('toaster', 'group')
+    expect(toaster).toHaveAttribute('position', 'top-center')
+    expect(toaster).toHaveAttribute('duration', '3000')
+    expect(toaster).toHaveAttribute('data-expand', 'true')
+    expect(toaster).toHaveAttribute('data-rich-colors', 'true')
+    expect(toaster).toHaveAttribute('data-close-button', 'true')
+  })
+})
\ No newline at end of file
diff --git a/web-app/src/constants/__tests__/windows.test.ts b/web-app/src/constants/__tests__/windows.test.ts
new file mode 100644
index 000000000..f9d388f98
--- /dev/null
+++ b/web-app/src/constants/__tests__/windows.test.ts
@@ -0,0 +1,36 @@
+import { describe, it, expect } from 'vitest'
+import { windowKey } from '../windows'
+
+describe('windows constants', () => {
+  it('should export correct window keys', () => {
+    expect(windowKey).toBeDefined()
+    expect(typeof windowKey).toBe('object')
+  })
+
+  it('should have logsAppWindow key', () => {
+    expect(windowKey.logsAppWindow).toBe('logs-app-window')
+  })
+
+  it('should have logsWindowLocalApiServer key', () => {
+    expect(windowKey.logsWindowLocalApiServer).toBe('logs-window-local-api-server')
+  })
+
+  it('should have systemMonitorWindow key', () => {
+    expect(windowKey.systemMonitorWindow).toBe('system-monitor-window')
+  })
+
+  it('should have all required keys', () => {
+    const expectedKeys = ['logsAppWindow', 'logsWindowLocalApiServer', 'systemMonitorWindow']
+    const actualKeys = Object.keys(windowKey)
+    
+    expect(actualKeys).toEqual(expect.arrayContaining(expectedKeys))
+    expect(actualKeys.length).toBe(expectedKeys.length)
+  })
+
+  it('should have string values for all keys', () => {
+    Object.values(windowKey).forEach(value => {
+      expect(typeof value).toBe('string')
+      expect(value.length).toBeGreaterThan(0)
+    })
+  })
+})
\ No newline at end of file
diff --git a/web-app/src/containers/__tests__/AvatarEmoji.test.tsx b/web-app/src/containers/__tests__/AvatarEmoji.test.tsx
new file mode 100644
index 000000000..ea44b95a0
--- /dev/null
+++ b/web-app/src/containers/__tests__/AvatarEmoji.test.tsx
@@ -0,0 +1,124 @@
+import { describe, it, expect } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import { AvatarEmoji } from '../AvatarEmoji'
+
+describe('AvatarEmoji Component', () => {
+  it('should return null when no avatar is provided', () => {
+    const { container } = render(<AvatarEmoji />)
+    expect(container.firstChild).toBeNull()
+  })
+
+  it('should return null when avatar is undefined', () => {
+    const { container } = render(<AvatarEmoji avatar={undefined} />)
+    expect(container.firstChild).toBeNull()
+  })
+
+  it('should render image when avatar is a custom image path', () => {
+    render(<AvatarEmoji avatar="/images/custom-avatar.png" />)
+    
+    const img = screen.getByRole('img')
+    expect(img).toBeDefined()
+    expect(img).toHaveAttribute('src', '/images/custom-avatar.png')
+    expect(img).toHaveAttribute('alt', 'Custom avatar')
+  })
+
+  it('should apply default image className', () => {
+    render(<AvatarEmoji avatar="/images/avatar.jpg" />)
+    
+    const img = screen.getByRole('img')
+    expect(img).toHaveClass('w-5', 'h-5', 'object-contain')
+  })
+
+  it('should apply custom image className', () => {
+    render(
+      <AvatarEmoji 
+        avatar="/images/avatar.jpg" 
+        imageClassName="w-10 h-10 rounded-full" 
+      />
+    )
+    
+    const img = screen.getByRole('img')
+    expect(img).toHaveClass('w-10', 'h-10', 'rounded-full')
+    expect(img).not.toHaveClass('w-5', 'h-5', 'object-contain')
+  })
+
+  it('should render emoji as text span', () => {
+    render(<AvatarEmoji avatar="🤖" />)
+    
+    const span = screen.getByText('🤖')
+    expect(span.tagName).toBe('SPAN')
+  })
+
+  it('should apply default text className for emoji', () => {
+    render(<AvatarEmoji avatar="😊" />)
+    
+    const span = screen.getByText('😊')
+    expect(span).toHaveClass('text-base')
+  })
+
+  it('should apply custom text className for emoji', () => {
+    render(
+      <AvatarEmoji 
+        avatar="🎯" 
+        textClassName="text-lg font-bold" 
+      />
+    )
+    
+    const span = screen.getByText('🎯')
+    expect(span).toHaveClass('text-lg', 'font-bold')
+    expect(span).not.toHaveClass('text-base')
+  })
+
+  it('should render text content as span', () => {
+    render(<AvatarEmoji avatar="AI" />)
+    
+    const span = screen.getByText('AI')
+    expect(span.tagName).toBe('SPAN')
+    expect(span).toHaveClass('text-base')
+  })
+
+  it('should handle React node as avatar', () => {
+    const customNode = <div data-testid="custom-node">Custom</div>
+    render(<AvatarEmoji avatar={customNode} />)
+    
+    const span = screen.getByText('Custom')
+    expect(span.closest('span')).toHaveClass('text-base')
+    expect(screen.getByTestId('custom-node')).toBeDefined()
+  })
+
+  it('should not treat non-image paths as custom images', () => {
+    render(<AvatarEmoji avatar="/api/data" />)
+    
+    const span = screen.getByText('/api/data')
+    expect(span.tagName).toBe('SPAN')
+    expect(screen.queryByRole('img')).toBeNull()
+  })
+
+  it('should not treat relative paths as custom images', () => {
+    render(<AvatarEmoji avatar="images/avatar.png" />)
+    
+    const span = screen.getByText('images/avatar.png')
+    expect(span.tagName).toBe('SPAN')
+    expect(screen.queryByRole('img')).toBeNull()
+  })
+
+  it('should handle different image extensions', () => {
+    const extensions = ['.png', '.jpg', '.jpeg', '.gif', '.svg']
+    
+    extensions.forEach((ext, index) => {
+      const { unmount } = render(<AvatarEmoji avatar={`/images/avatar${ext}`} />)
+      
+      const img = screen.getByRole('img')
+      expect(img).toHaveAttribute('src', `/images/avatar${ext}`)
+      
+      unmount()
+    })
+  })
+
+  it('should maintain accessibility for custom images', () => {
+    render(<AvatarEmoji avatar="/images/user-avatar.png" />)
+    
+    const img = screen.getByRole('img')
+    expect(img).toHaveAttribute('alt', 'Custom avatar')
+  })
+})
\ No newline at end of file
diff --git a/web-app/src/hooks/__tests__/useTheme.test.ts b/web-app/src/hooks/__tests__/useTheme.test.ts
new file mode 100644
index 000000000..a2416eb03
--- /dev/null
+++ b/web-app/src/hooks/__tests__/useTheme.test.ts
@@ -0,0 +1,189 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { renderHook, act } from '@testing-library/react'
+import { checkOSDarkMode } from '../useTheme'
+
+// Mock Tauri API
+vi.mock('@tauri-apps/api/window', () => ({
+  getCurrentWindow: () => ({
+    setTheme: vi.fn().mockResolvedValue(undefined),
+  }),
+  Theme: {
+    Dark: 'dark',
+    Light: 'light',
+  },
+}))
+
+// Mock localStorage
+vi.mock('@/constants/localStorage', () => ({
+  localStorageKey: {
+    theme: 'theme',
+  },
+}))
+
+// Mock zustand persist
+vi.mock('zustand/middleware', () => ({
+  persist: (fn: any) => fn,
+  createJSONStorage: () => ({
+    getItem: vi.fn(),
+    setItem: vi.fn(),
+    removeItem: vi.fn(),
+  }),
+}))
+
+describe('useTheme', () => {
+  let originalMatchMedia: any
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+    // Mock window.matchMedia
+    originalMatchMedia = window.matchMedia
+    window.matchMedia = vi.fn()
+  })
+
+  afterEach(() => {
+    // Restore original matchMedia
+    window.matchMedia = originalMatchMedia
+  })
+
+  describe('checkOSDarkMode', () => {
+    it('should return true when OS prefers dark mode', () => {
+      vi.mocked(window.matchMedia).mockReturnValue({
+        matches: true,
+        addEventListener: vi.fn(),
+        removeEventListener: vi.fn(),
+      } as any)
+
+      const result = checkOSDarkMode()
+      expect(result).toBe(true)
+      expect(window.matchMedia).toHaveBeenCalledWith('(prefers-color-scheme: dark)')
+    })
+
+    it('should return false when OS prefers light mode', () => {
+      vi.mocked(window.matchMedia).mockReturnValue({
+        matches: false,
+        addEventListener: vi.fn(),
+        removeEventListener: vi.fn(),
+      } as any)
+
+      const result = checkOSDarkMode()
+      expect(result).toBe(false)
+    })
+
+    it('should return falsy when matchMedia is not available', () => {
+      const originalMatchMedia = window.matchMedia
+      // @ts-ignore
+      window.matchMedia = null
+
+      const result = checkOSDarkMode()
+      expect(result).toBeFalsy()
+      
+      // Restore
+      window.matchMedia = originalMatchMedia
+    })
+  })
+
+  describe('useTheme hook basic functionality', () => {
+    beforeEach(() => {
+      // Default to light mode
+      vi.mocked(window.matchMedia).mockReturnValue({
+        matches: false,
+        addEventListener: vi.fn(),
+        removeEventListener: vi.fn(),
+      } as any)
+    })
+
+    it('should have the expected interface', async () => {
+      const { useTheme } = await import('../useTheme')
+      const { result } = renderHook(() => useTheme())
+
+      expect(result.current).toHaveProperty('activeTheme')
+      expect(result.current).toHaveProperty('isDark')
+      expect(result.current).toHaveProperty('setTheme')
+      expect(result.current).toHaveProperty('setIsDark')
+      expect(typeof result.current.setTheme).toBe('function')
+      expect(typeof result.current.setIsDark).toBe('function')
+    })
+
+    it('should initialize with auto theme', async () => {
+      const { useTheme } = await import('../useTheme')
+      const { result } = renderHook(() => useTheme())
+
+      expect(result.current.activeTheme).toBe('auto')
+      expect(typeof result.current.isDark).toBe('boolean')
+    })
+
+    it('should allow setting isDark directly', async () => {
+      const { useTheme } = await import('../useTheme')
+      const { result } = renderHook(() => useTheme())
+
+      act(() => {
+        result.current.setIsDark(true)
+      })
+
+      expect(result.current.isDark).toBe(true)
+
+      act(() => {
+        result.current.setIsDark(false)
+      })
+
+      expect(result.current.isDark).toBe(false)
+    })
+
+    it('should handle theme changes', async () => {
+      const { useTheme } = await import('../useTheme')
+      const { result } = renderHook(() => useTheme())
+
+      await act(async () => {
+        await result.current.setTheme('dark')
+      })
+
+      expect(result.current.activeTheme).toBe('dark')
+      expect(result.current.isDark).toBe(true)
+
+      await act(async () => {
+        await result.current.setTheme('light')
+      })
+
+      expect(result.current.activeTheme).toBe('light')
+      expect(result.current.isDark).toBe(false)
+    })
+
+    it('should handle auto theme with OS preference', async () => {
+      // Mock OS dark preference
+      vi.mocked(window.matchMedia).mockReturnValue({
+        matches: true,
+        addEventListener: vi.fn(),
+        removeEventListener: vi.fn(),
+      } as any)
+
+      const { useTheme } = await import('../useTheme')
+      const { result } = renderHook(() => useTheme())
+
+      await act(async () => {
+        await result.current.setTheme('auto')
+      })
+
+      expect(result.current.activeTheme).toBe('auto')
+      expect(result.current.isDark).toBe(true)
+    })
+
+    it('should handle auto theme with light OS preference', async () => {
+      // Mock OS light preference
+      vi.mocked(window.matchMedia).mockReturnValue({
+        matches: false,
+        addEventListener: vi.fn(),
+        removeEventListener: vi.fn(),
+      } as any)
+
+      const { useTheme } = await import('../useTheme')
+      const { result } = renderHook(() => useTheme())
+
+      await act(async () => {
+        await result.current.setTheme('auto')
+      })
+
+      expect(result.current.activeTheme).toBe('auto')
+      expect(result.current.isDark).toBe(false)
+    })
+  })
+})
\ No newline at end of file
diff --git a/web-app/src/services/__tests__/analytic.test.ts b/web-app/src/services/__tests__/analytic.test.ts
new file mode 100644
index 000000000..94f3fa7e9
--- /dev/null
+++ b/web-app/src/services/__tests__/analytic.test.ts
@@ -0,0 +1,265 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { updateDistinctId, getAppDistinctId } from '../analytic'
+
+// Mock window.core API
+const mockGetAppConfigurations = vi.fn()
+const mockUpdateAppConfiguration = vi.fn()
+
+const mockCore = {
+  api: {
+    getAppConfigurations: mockGetAppConfigurations,
+    updateAppConfiguration: mockUpdateAppConfiguration,
+  },
+}
+
+// Setup global window mock
+Object.defineProperty(window, 'core', {
+  writable: true,
+  value: mockCore,
+})
+
+describe('analytic service', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  describe('updateDistinctId', () => {
+    it('should update distinct id in app configuration', async () => {
+      const mockConfiguration = {
+        distinct_id: 'old-id',
+        other_setting: 'value',
+      }
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      mockUpdateAppConfiguration.mockResolvedValue(undefined)
+      
+      await updateDistinctId('new-distinct-id')
+      
+      expect(mockGetAppConfigurations).toHaveBeenCalledTimes(1)
+      expect(mockUpdateAppConfiguration).toHaveBeenCalledWith({
+        configuration: {
+          distinct_id: 'new-distinct-id',
+          other_setting: 'value',
+        },
+      })
+    })
+
+    it('should handle when configuration has no existing distinct_id', async () => {
+      const mockConfiguration = {
+        other_setting: 'value',
+      }
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      mockUpdateAppConfiguration.mockResolvedValue(undefined)
+      
+      await updateDistinctId('first-distinct-id')
+      
+      expect(mockUpdateAppConfiguration).toHaveBeenCalledWith({
+        configuration: {
+          distinct_id: 'first-distinct-id',
+          other_setting: 'value',
+        },
+      })
+    })
+
+    it('should handle empty string as distinct id', async () => {
+      const mockConfiguration = {
+        distinct_id: 'old-id',
+      }
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      mockUpdateAppConfiguration.mockResolvedValue(undefined)
+      
+      await updateDistinctId('')
+      
+      expect(mockUpdateAppConfiguration).toHaveBeenCalledWith({
+        configuration: {
+          distinct_id: '',
+        },
+      })
+    })
+
+    it('should handle UUID format distinct id', async () => {
+      const mockConfiguration = {}
+      const uuidId = '550e8400-e29b-41d4-a716-446655440000'
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      mockUpdateAppConfiguration.mockResolvedValue(undefined)
+      
+      await updateDistinctId(uuidId)
+      
+      expect(mockUpdateAppConfiguration).toHaveBeenCalledWith({
+        configuration: {
+          distinct_id: uuidId,
+        },
+      })
+    })
+
+    it('should handle API errors gracefully', async () => {
+      mockGetAppConfigurations.mockRejectedValue(new Error('API Error'))
+      
+      await expect(updateDistinctId('test-id')).rejects.toThrow('API Error')
+      expect(mockUpdateAppConfiguration).not.toHaveBeenCalled()
+    })
+
+    it('should handle update configuration errors', async () => {
+      const mockConfiguration = { distinct_id: 'old-id' }
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      mockUpdateAppConfiguration.mockRejectedValue(new Error('Update Error'))
+      
+      await expect(updateDistinctId('new-id')).rejects.toThrow('Update Error')
+    })
+  })
+
+  describe('getAppDistinctId', () => {
+    it('should return distinct id from app configuration', async () => {
+      const mockConfiguration = {
+        distinct_id: 'test-distinct-id',
+        other_setting: 'value',
+      }
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      
+      const result = await getAppDistinctId()
+      
+      expect(result).toBe('test-distinct-id')
+      expect(mockGetAppConfigurations).toHaveBeenCalledTimes(1)
+    })
+
+    it('should return undefined when distinct_id is not set', async () => {
+      const mockConfiguration = {
+        other_setting: 'value',
+      }
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      
+      const result = await getAppDistinctId()
+      
+      expect(result).toBeUndefined()
+    })
+
+    it('should return empty string if distinct_id is empty', async () => {
+      const mockConfiguration = {
+        distinct_id: '',
+      }
+      
+      mockGetAppConfigurations.mockResolvedValue(mockConfiguration)
+      
+      const result = await getAppDistinctId()
+      
+      expect(result).toBe('')
+    })
+
+    it('should handle null configuration', async () => {
+      mockGetAppConfigurations.mockResolvedValue(null)
+      
+      await expect(getAppDistinctId()).rejects.toThrow()
+    })
+
+    it('should handle undefined configuration', async () => {
+      mockGetAppConfigurations.mockResolvedValue(undefined)
+      
+      await expect(getAppDistinctId()).rejects.toThrow()
+    })
+
+    it('should handle API errors', async () => {
+      mockGetAppConfigurations.mockRejectedValue(new Error('Get Config Error'))
+      
+      await expect(getAppDistinctId()).rejects.toThrow('Get Config Error')
+    })
+
+    it('should handle different types of distinct_id values', async () => {
+      // Test with UUID
+      mockGetAppConfigurations.mockResolvedValue({
+        distinct_id: '550e8400-e29b-41d4-a716-446655440000',
+      })
+      
+      let result = await getAppDistinctId()
+      expect(result).toBe('550e8400-e29b-41d4-a716-446655440000')
+      
+      // Test with simple string
+      mockGetAppConfigurations.mockResolvedValue({
+        distinct_id: 'user123',
+      })
+      
+      result = await getAppDistinctId()
+      expect(result).toBe('user123')
+      
+      // Test with numeric string
+      mockGetAppConfigurations.mockResolvedValue({
+        distinct_id: '12345',
+      })
+      
+      result = await getAppDistinctId()
+      expect(result).toBe('12345')
+    })
+  })
+
+  describe('integration tests', () => {
+    it('should update and retrieve distinct id', async () => {
+      const newId = 'integration-test-id'
+      const mockConfiguration = { other_setting: 'value' }
+      
+      // Mock get configuration for update
+      mockGetAppConfigurations.mockResolvedValueOnce(mockConfiguration)
+      mockUpdateAppConfiguration.mockResolvedValue(undefined)
+      
+      // Mock get configuration for retrieval
+      mockGetAppConfigurations.mockResolvedValueOnce({
+        ...mockConfiguration,
+        distinct_id: newId,
+      })
+      
+      // Update the distinct id
+      await updateDistinctId(newId)
+      
+      // Retrieve the distinct id
+      const retrievedId = await getAppDistinctId()
+      
+      expect(retrievedId).toBe(newId)
+      expect(mockGetAppConfigurations).toHaveBeenCalledTimes(2)
+      expect(mockUpdateAppConfiguration).toHaveBeenCalledTimes(1)
+    })
+  })
+
+  describe('edge cases', () => {
+    it('should handle when window.core is undefined', async () => {
+      const originalCore = window.core
+      
+      // Temporarily remove core
+      Object.defineProperty(window, 'core', {
+        writable: true,
+        value: undefined,
+      })
+      
+      await expect(updateDistinctId('test')).rejects.toThrow()
+      await expect(getAppDistinctId()).rejects.toThrow()
+      
+      // Restore core
+      Object.defineProperty(window, 'core', {
+        writable: true,
+        value: originalCore,
+      })
+    })
+
+    it('should handle when window.core.api is undefined', async () => {
+      const originalCore = window.core
+      
+      // Set core without api
+      Object.defineProperty(window, 'core', {
+        writable: true,
+        value: {},
+      })
+      
+      await expect(updateDistinctId('test')).rejects.toThrow()
+      await expect(getAppDistinctId()).rejects.toThrow()
+      
+      // Restore core
+      Object.defineProperty(window, 'core', {
+        writable: true,
+        value: originalCore,
+      })
+    })
+  })
+})
\ No newline at end of file
diff --git a/web-app/src/services/__tests__/events.test.ts b/web-app/src/services/__tests__/events.test.ts
new file mode 100644
index 000000000..88a6c9a8c
--- /dev/null
+++ b/web-app/src/services/__tests__/events.test.ts
@@ -0,0 +1,247 @@
+import { describe, it, expect, vi } from 'vitest'
+import { EventEmitter } from '../events'
+
+describe('EventEmitter', () => {
+  let eventEmitter: EventEmitter
+
+  beforeEach(() => {
+    eventEmitter = new EventEmitter()
+  })
+
+  describe('constructor', () => {
+    it('should create an instance with empty handlers map', () => {
+      expect(eventEmitter).toBeInstanceOf(EventEmitter)
+      expect(eventEmitter['handlers']).toBeInstanceOf(Map)
+      expect(eventEmitter['handlers'].size).toBe(0)
+    })
+  })
+
+  describe('on method', () => {
+    it('should register a handler for a new event', () => {
+      const handler = vi.fn()
+      
+      eventEmitter.on('test-event', handler)
+      
+      expect(eventEmitter['handlers'].has('test-event')).toBe(true)
+      expect(eventEmitter['handlers'].get('test-event')).toContain(handler)
+    })
+
+    it('should add multiple handlers for the same event', () => {
+      const handler1 = vi.fn()
+      const handler2 = vi.fn()
+      
+      eventEmitter.on('test-event', handler1)
+      eventEmitter.on('test-event', handler2)
+      
+      const handlers = eventEmitter['handlers'].get('test-event')
+      expect(handlers).toHaveLength(2)
+      expect(handlers).toContain(handler1)
+      expect(handlers).toContain(handler2)
+    })
+
+    it('should handle multiple different events', () => {
+      const handler1 = vi.fn()
+      const handler2 = vi.fn()
+      
+      eventEmitter.on('event1', handler1)
+      eventEmitter.on('event2', handler2)
+      
+      expect(eventEmitter['handlers'].has('event1')).toBe(true)
+      expect(eventEmitter['handlers'].has('event2')).toBe(true)
+      expect(eventEmitter['handlers'].get('event1')).toContain(handler1)
+      expect(eventEmitter['handlers'].get('event2')).toContain(handler2)
+    })
+
+    it('should allow the same handler to be registered multiple times', () => {
+      const handler = vi.fn()
+      
+      eventEmitter.on('test-event', handler)
+      eventEmitter.on('test-event', handler)
+      
+      const handlers = eventEmitter['handlers'].get('test-event')
+      expect(handlers).toHaveLength(2)
+      expect(handlers![0]).toBe(handler)
+      expect(handlers![1]).toBe(handler)
+    })
+  })
+
+  describe('off method', () => {
+    it('should remove a handler from an existing event', () => {
+      const handler = vi.fn()
+      
+      eventEmitter.on('test-event', handler)
+      expect(eventEmitter['handlers'].get('test-event')).toContain(handler)
+      
+      eventEmitter.off('test-event', handler)
+      expect(eventEmitter['handlers'].get('test-event')).not.toContain(handler)
+    })
+
+    it('should do nothing when trying to remove handler from non-existent event', () => {
+      const handler = vi.fn()
+      
+      // Should not throw an error
+      expect(() => {
+        eventEmitter.off('non-existent-event', handler)
+      }).not.toThrow()
+    })
+
+    it('should do nothing when trying to remove non-existent handler', () => {
+      const handler1 = vi.fn()
+      const handler2 = vi.fn()
+      
+      eventEmitter.on('test-event', handler1)
+      
+      // Should not throw an error
+      expect(() => {
+        eventEmitter.off('test-event', handler2)
+      }).not.toThrow()
+      
+      // Original handler should still be there
+      expect(eventEmitter['handlers'].get('test-event')).toContain(handler1)
+    })
+
+    it('should remove only the first occurrence of a handler', () => {
+      const handler = vi.fn()
+      
+      eventEmitter.on('test-event', handler)
+      eventEmitter.on('test-event', handler)
+      
+      expect(eventEmitter['handlers'].get('test-event')).toHaveLength(2)
+      
+      eventEmitter.off('test-event', handler)
+      
+      expect(eventEmitter['handlers'].get('test-event')).toHaveLength(1)
+      expect(eventEmitter['handlers'].get('test-event')).toContain(handler)
+    })
+
+    it('should remove correct handler when multiple handlers exist', () => {
+      const handler1 = vi.fn()
+      const handler2 = vi.fn()
+      const handler3 = vi.fn()
+      
+      eventEmitter.on('test-event', handler1)
+      eventEmitter.on('test-event', handler2)
+      eventEmitter.on('test-event', handler3)
+      
+      eventEmitter.off('test-event', handler2)
+      
+      const handlers = eventEmitter['handlers'].get('test-event')
+      expect(handlers).toHaveLength(2)
+      expect(handlers).toContain(handler1)
+      expect(handlers).not.toContain(handler2)
+      expect(handlers).toContain(handler3)
+    })
+  })
+
+  describe('emit method', () => {
+    it('should call all handlers for an event', () => {
+      const handler1 = vi.fn()
+      const handler2 = vi.fn()
+      
+      eventEmitter.on('test-event', handler1)
+      eventEmitter.on('test-event', handler2)
+      
+      eventEmitter.emit('test-event', 'test-data')
+      
+      expect(handler1).toHaveBeenCalledWith('test-data')
+      expect(handler2).toHaveBeenCalledWith('test-data')
+    })
+
+    it('should do nothing when emitting non-existent event', () => {
+      // Should not throw an error
+      expect(() => {
+        eventEmitter.emit('non-existent-event', 'data')
+      }).not.toThrow()
+    })
+
+    it('should pass arguments to handlers', () => {
+      const handler = vi.fn()
+      const testData = { message: 'test', number: 42 }
+      
+      eventEmitter.on('test-event', handler)
+      eventEmitter.emit('test-event', testData)
+      
+      expect(handler).toHaveBeenCalledWith(testData)
+    })
+
+    it('should call handlers in the order they were added', () => {
+      const callOrder: number[] = []
+      const handler1 = vi.fn(() => callOrder.push(1))
+      const handler2 = vi.fn(() => callOrder.push(2))
+      const handler3 = vi.fn(() => callOrder.push(3))
+      
+      eventEmitter.on('test-event', handler1)
+      eventEmitter.on('test-event', handler2)
+      eventEmitter.on('test-event', handler3)
+      
+      eventEmitter.emit('test-event', null)
+      
+      expect(callOrder).toEqual([1, 2, 3])
+    })
+
+    it('should handle null and undefined arguments', () => {
+      const handler = vi.fn()
+      
+      eventEmitter.on('test-event', handler)
+      
+      eventEmitter.emit('test-event', null)
+      expect(handler).toHaveBeenCalledWith(null)
+      
+      eventEmitter.emit('test-event', undefined)
+      expect(handler).toHaveBeenCalledWith(undefined)
+    })
+
+    it('should not affect other events', () => {
+      const handler1 = vi.fn()
+      const handler2 = vi.fn()
+      
+      eventEmitter.on('event1', handler1)
+      eventEmitter.on('event2', handler2)
+      
+      eventEmitter.emit('event1', 'data1')
+      
+      expect(handler1).toHaveBeenCalledWith('data1')
+      expect(handler2).not.toHaveBeenCalled()
+    })
+  })
+
+  describe('integration tests', () => {
+    it('should support complete event lifecycle', () => {
+      const handler1 = vi.fn()
+      const handler2 = vi.fn()
+      
+      // Register handlers
+      eventEmitter.on('lifecycle-event', handler1)
+      eventEmitter.on('lifecycle-event', handler2)
+      
+      // Emit event
+      eventEmitter.emit('lifecycle-event', 'test-data')
+      expect(handler1).toHaveBeenCalledWith('test-data')
+      expect(handler2).toHaveBeenCalledWith('test-data')
+      
+      // Remove one handler
+      eventEmitter.off('lifecycle-event', handler1)
+      
+      // Emit again
+      eventEmitter.emit('lifecycle-event', 'test-data-2')
+      expect(handler1).toHaveBeenCalledTimes(1) // Still only called once
+      expect(handler2).toHaveBeenCalledTimes(2) // Called twice
+      expect(handler2).toHaveBeenLastCalledWith('test-data-2')
+    })
+
+    it('should handle complex data types', () => {
+      const handler = vi.fn()
+      const complexData = {
+        array: [1, 2, 3],
+        object: { nested: true },
+        function: () => 'test',
+        symbol: Symbol('test'),
+      }
+      
+      eventEmitter.on('complex-event', handler)
+      eventEmitter.emit('complex-event', complexData)
+      
+      expect(handler).toHaveBeenCalledWith(complexData)
+    })
+  })
+})
\ No newline at end of file