Dark mode support, theme switching, and dynamic UI states are features that AI coding tools handle superficially. The AI generates CSS that looks correct in the default theme and breaks in alternatives.

Common visual state bugs AI introduces: text invisible against same-color background in dark mode, icons that don't invert, borders that disappear, focus indicators invisible on dark backgrounds, charts with hardcoded colors that clash with theme, and modals with wrong background transparency.

These bugs are invisible during development if the developer only tests in light mode (most do). They're immediately visible to users who prefer dark mode — which is roughly 80% of developers and an increasing percentage of general users.

What to Test

• Every page renders correctly in both light and dark mode

• Interactive elements (buttons, links, form fields) are visible and accessible in all themes

• Focus indicators contrast against all background colors

• Data visualizations use theme-aware colors

• Images and icons adapt to theme (or have sufficient contrast in both)

• Theme switching doesn't break layout or state

• User's theme preference persists across sessions

TestSprite's visual verification catches rendering issues across UI states. When the agent navigates your application, it validates that elements are visible, correctly positioned, and visually accessible. Theme-specific rendering bugs are caught on the PR before users see them.

Dark mode isn't a nice-to-have anymore. It's expected. Test it.

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