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552/**
* Real Browser Environment Dark Mode Flicker Test
*
* This test attempts to simulate real browser refresh scenarios including:
* 1. SSR HTML generation phase
* 2. Client-side JavaScript loading
* 3. Theme system initialization
* 4. CSS styles application timing
*/
import { render, screen, waitFor } from '@testing-library/react'
import { ThemeProvider } from 'next-themes'
import { useEffect, useState } from 'react'
import useTheme from '@/hooks/use-theme'
const DARK_MODE_MEDIA_QUERY = /prefers-color-scheme:\s*dark/i
// Setup browser environment for testing
const setupMockEnvironment = (storedTheme: string | null, systemPrefersDark = false) => {
if (typeof window === 'undefined')
return
try {
window.localStorage.clear()
}
catch {
// ignore if localStorage has been replaced by a throwing stub
}
if (storedTheme === null)
window.localStorage.removeItem('theme')
else
window.localStorage.setItem('theme', storedTheme)
document.documentElement.removeAttribute('data-theme')
const mockMatchMedia: typeof window.matchMedia = (query: string) => {
const listeners = new Set<(event: MediaQueryListEvent) => void>()
const isDarkQuery = DARK_MODE_MEDIA_QUERY.test(query)
const matches = isDarkQuery ? systemPrefersDark : false
const handleAddListener = (listener: (event: MediaQueryListEvent) => void) => {
listeners.add(listener)
}
const handleRemoveListener = (listener: (event: MediaQueryListEvent) => void) => {
listeners.delete(listener)
}
const handleAddEventListener = (_event: string, listener: EventListener) => {
if (typeof listener === 'function')
listeners.add(listener as (event: MediaQueryListEvent) => void)
}
const handleRemoveEventListener = (_event: string, listener: EventListener) => {
if (typeof listener === 'function')
listeners.delete(listener as (event: MediaQueryListEvent) => void)
}
const handleDispatchEvent = (event: Event) => {
listeners.forEach(listener => listener(event as MediaQueryListEvent))
return true
}
const mediaQueryList: MediaQueryList = {
matches,
media: query,
onchange: null,
addListener: handleAddListener,
removeListener: handleRemoveListener,
addEventListener: handleAddEventListener,
removeEventListener: handleRemoveEventListener,
dispatchEvent: handleDispatchEvent,
}
return mediaQueryList
}
vi.spyOn(window, 'matchMedia').mockImplementation(mockMatchMedia)
}
// Helper function to create timing page component
const createTimingPageComponent = (
timingData: Array<{ phase: string, timestamp: number, styles: { backgroundColor: string, color: string } }>,
) => {
const recordTiming = (phase: string, styles: { backgroundColor: string, color: string }) => {
timingData.push({
phase,
timestamp: performance.now(),
styles,
})
}
const TimingPageComponent = () => {
const [mounted, setMounted] = useState(false)
const { theme } = useTheme()
const isDark = mounted ? theme === 'dark' : false
const currentStyles = {
backgroundColor: isDark ? '#1f2937' : '#ffffff',
color: isDark ? '#ffffff' : '#000000',
}
recordTiming(mounted ? 'CSR' : 'Initial', currentStyles)
useEffect(() => {
setMounted(true)
}, [])
return (
<div
data-testid="timing-page"
style={currentStyles}
>
<div data-testid="timing-status">
Phase:
{' '}
{mounted ? 'CSR' : 'Initial'}
{' '}
| Theme:
{' '}
{theme}
{' '}
| Visual:
{' '}
{isDark ? 'dark' : 'light'}
</div>
</div>
)
}
return TimingPageComponent
}
// Helper function to create CSS test component
const createCSSTestComponent = (
cssStates: Array<{ className: string, timestamp: number }>,
) => {
const recordCSSState = (className: string) => {
cssStates.push({
className,
timestamp: performance.now(),
})
}
const CSSTestComponent = () => {
const [mounted, setMounted] = useState(false)
const { theme } = useTheme()
const isDark = mounted ? theme === 'dark' : false
const className = `min-h-screen ${isDark ? 'bg-gray-900 text-white' : 'bg-white text-black'}`
recordCSSState(className)
useEffect(() => {
setMounted(true)
}, [])
return (
<div
data-testid="css-component"
className={className}
>
<div data-testid="css-classes">
Classes:
{className}
</div>
</div>
)
}
return CSSTestComponent
}
// Helper function to create performance test component
const createPerformanceTestComponent = (
performanceMarks: Array<{ event: string, timestamp: number }>,
) => {
const recordPerformanceMark = (event: string) => {
performanceMarks.push({ event, timestamp: performance.now() })
}
const PerformanceTestComponent = () => {
const [mounted, setMounted] = useState(false)
const { theme } = useTheme()
recordPerformanceMark('component-render')
useEffect(() => {
recordPerformanceMark('mount-start')
setMounted(true)
recordPerformanceMark('mount-complete')
}, [])
useEffect(() => {
if (theme)
recordPerformanceMark('theme-available')
}, [theme])
return (
<div data-testid="performance-test">
Mounted:
{' '}
{mounted.toString()}
{' '}
| Theme:
{' '}
{theme || 'loading'}
</div>
)
}
return PerformanceTestComponent
}
// Simulate real page component based on Dify's actual theme usage
const PageComponent = () => {
const [mounted, setMounted] = useState(false)
const { theme } = useTheme()
useEffect(() => {
setMounted(true)
}, [])
// Simulate common theme usage pattern in Dify
const isDark = mounted ? theme === 'dark' : false
return (
<div data-theme={isDark ? 'dark' : 'light'}>
<div
data-testid="page-content"
style={{ backgroundColor: isDark ? '#1f2937' : '#ffffff' }}
>
<h1 style={{ color: isDark ? '#ffffff' : '#000000' }}>
Dify Application
</h1>
<div data-testid="theme-indicator">
Current Theme:
{' '}
{mounted ? theme : 'unknown'}
</div>
<div data-testid="visual-appearance">
Appearance:
{' '}
{isDark ? 'dark' : 'light'}
</div>
</div>
</div>
)
}
const TestThemeProvider = ({ children }: { children: React.ReactNode }) => (
<ThemeProvider
attribute="data-theme"
defaultTheme="system"
enableSystem
disableTransitionOnChange
enableColorScheme={false}
>
{children}
</ThemeProvider>
)
describe('Real Browser Environment Dark Mode Flicker Test', () => {
beforeEach(() => {
vi.restoreAllMocks()
vi.clearAllMocks()
if (typeof window !== 'undefined') {
try {
window.localStorage.clear()
}
catch {
// ignore when localStorage is replaced with an error-throwing stub
}
document.documentElement.removeAttribute('data-theme')
}
})
describe('Page Refresh Scenario Simulation', () => {
it('simulates complete page loading process with dark theme', async () => {
// Setup: User previously selected dark mode
setupMockEnvironment('dark')
render(
<TestThemeProvider>
<PageComponent />
</TestThemeProvider>,
)
// Check initial client-side rendering state
const initialState = {
theme: screen.getByTestId('theme-indicator').textContent,
appearance: screen.getByTestId('visual-appearance').textContent,
}
console.log('Initial client state:', initialState)
// Wait for theme system to fully initialize
await waitFor(() => {
expect(screen.getByTestId('theme-indicator')).toHaveTextContent('Current Theme: dark')
})
const finalState = {
theme: screen.getByTestId('theme-indicator').textContent,
appearance: screen.getByTestId('visual-appearance').textContent,
}
console.log('Final state:', finalState)
// Document the state change - this is the source of flicker
console.log('State change detection: Initial -> Final')
})
it('handles light theme correctly', async () => {
setupMockEnvironment('light')
render(
<TestThemeProvider>
<PageComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('theme-indicator')).toHaveTextContent('Current Theme: light')
})
expect(screen.getByTestId('visual-appearance')).toHaveTextContent('Appearance: light')
})
it('handles system theme with dark preference', async () => {
setupMockEnvironment('system', true) // system theme, dark preference
render(
<TestThemeProvider>
<PageComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('theme-indicator')).toHaveTextContent('Current Theme: dark')
})
expect(screen.getByTestId('visual-appearance')).toHaveTextContent('Appearance: dark')
})
it('handles system theme with light preference', async () => {
setupMockEnvironment('system', false) // system theme, light preference
render(
<TestThemeProvider>
<PageComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('theme-indicator')).toHaveTextContent('Current Theme: light')
})
expect(screen.getByTestId('visual-appearance')).toHaveTextContent('Appearance: light')
})
it('handles no stored theme (defaults to system)', async () => {
setupMockEnvironment(null, false) // no stored theme, system prefers light
render(
<TestThemeProvider>
<PageComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('theme-indicator')).toHaveTextContent('Current Theme: light')
})
})
it('measures timing window of style changes', async () => {
setupMockEnvironment('dark')
const timingData: Array<{ phase: string, timestamp: number, styles: any }> = []
const TimingPageComponent = createTimingPageComponent(timingData)
render(
<TestThemeProvider>
<TimingPageComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('timing-status')).toHaveTextContent('Phase: CSR')
})
// Analyze timing and style changes
console.log('\n=== Style Change Timeline ===')
timingData.forEach((data, index) => {
console.log(`${index + 1}. ${data.phase}: bg=${data.styles.backgroundColor}, color=${data.styles.color}`)
})
// Check if there are style changes (this is visible flicker)
const hasStyleChange = timingData.length > 1
&& timingData[0].styles.backgroundColor !== timingData[timingData.length - 1].styles.backgroundColor
if (hasStyleChange)
console.log('⚠️ Style changes detected - this causes visible flicker')
else
console.log('✅ No style changes detected')
expect(timingData.length).toBeGreaterThan(1)
})
})
describe('CSS Application Timing Tests', () => {
it('checks CSS class changes causing flicker', async () => {
setupMockEnvironment('dark')
const cssStates: Array<{ className: string, timestamp: number }> = []
const CSSTestComponent = createCSSTestComponent(cssStates)
render(
<TestThemeProvider>
<CSSTestComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('css-classes')).toHaveTextContent('bg-gray-900 text-white')
})
console.log('\n=== CSS Class Change Detection ===')
cssStates.forEach((state, index) => {
console.log(`${index + 1}. ${state.className}`)
})
// Check if CSS classes have changed
const hasCSSChange = cssStates.length > 1
&& cssStates[0].className !== cssStates[cssStates.length - 1].className
if (hasCSSChange) {
console.log('⚠️ CSS class changes detected - may cause style flicker')
console.log(`From: "${cssStates[0].className}"`)
console.log(`To: "${cssStates[cssStates.length - 1].className}"`)
}
expect(hasCSSChange).toBe(true) // We expect to see this change
})
})
describe('Edge Cases and Error Handling', () => {
it('handles localStorage access errors gracefully', async () => {
setupMockEnvironment(null)
const mockStorage = {
getItem: vi.fn(() => {
throw new Error('LocalStorage access denied')
}),
setItem: vi.fn(),
removeItem: vi.fn(),
clear: vi.fn(),
}
Object.defineProperty(window, 'localStorage', {
value: mockStorage,
configurable: true,
})
try {
render(
<TestThemeProvider>
<PageComponent />
</TestThemeProvider>,
)
// Should fallback gracefully without crashing
await waitFor(() => {
expect(screen.getByTestId('theme-indicator')).toBeInTheDocument()
})
// Should default to light theme when localStorage fails
expect(screen.getByTestId('visual-appearance')).toHaveTextContent('Appearance: light')
}
finally {
Reflect.deleteProperty(window, 'localStorage')
}
})
it('handles invalid theme values in localStorage', async () => {
setupMockEnvironment('invalid-theme-value')
render(
<TestThemeProvider>
<PageComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('theme-indicator')).toBeInTheDocument()
})
// Should handle invalid values gracefully
const themeIndicator = screen.getByTestId('theme-indicator')
expect(themeIndicator).toBeInTheDocument()
})
})
describe('Performance and Regression Tests', () => {
it('verifies ThemeProvider position fix reduces initialization delay', async () => {
const performanceMarks: Array<{ event: string, timestamp: number }> = []
setupMockEnvironment('dark')
expect(window.localStorage.getItem('theme')).toBe('dark')
const PerformanceTestComponent = createPerformanceTestComponent(performanceMarks)
render(
<TestThemeProvider>
<PerformanceTestComponent />
</TestThemeProvider>,
)
await waitFor(() => {
expect(screen.getByTestId('performance-test')).toHaveTextContent('Theme: dark')
})
// Analyze performance timeline
console.log('\n=== Performance Timeline ===')
performanceMarks.forEach((mark) => {
console.log(`${mark.event}: ${mark.timestamp.toFixed(2)}ms`)
})
expect(performanceMarks.length).toBeGreaterThan(3)
})
})
describe('Solution Requirements Definition', () => {
it('defines technical requirements to eliminate flicker', () => {
const technicalRequirements = {
ssrConsistency: 'SSR and CSR must render identical initial styles',
synchronousDetection: 'Theme detection must complete synchronously before first render',
noStyleChanges: 'No visible style changes should occur after hydration',
performanceImpact: 'Solution should not significantly impact page load performance',
browserCompatibility: 'Must work consistently across all major browsers',
}
console.log('\n=== Technical Requirements ===')
Object.entries(technicalRequirements).forEach(([key, requirement]) => {
console.log(`${key}: ${requirement}`)
expect(requirement).toBeDefined()
})
// A successful solution should pass all these requirements
})
})
})