Most component libraries are tested against the same three inputs: a short title, a two-sentence description, and a placeholder image at whatever size the designer used in Figma. That covers the happy path and almost nothing else. Below are twelve specific content shapes worth testing before a component ships to a design system, roughly ordered from cheapest to check to most commonly skipped.
The shortest realistic string
Not an empty string, the shortest thing a real user or editor would actually enter. A one-word title, a one-line description. Reveals whether your flex or grid layout collapses awkwardly when content is minimal.
The longest realistic string
Not an infinite stress-test string, the longest value your content model or character limit actually permits. Reveals truncation, wrapping, and overflow behaviour at the real ceiling, not an artificial one.
A string with no natural break points
A long unbroken word, a URL, an email address, a hyphenated technical term. Reveals whether overflow-wrap or word-break is actually set, since a component tested only with normal prose never surfaces this.
Two adjacent headings with no paragraph between them
An H2 immediately followed by an H3, or two H2s in a row. Reveals margin-collapse and spacing bugs that only appear when headings sit next to each other instead of always being separated by body text.
A four- or five-line paragraph in a narrow column
A single sentence never reveals line-height on a second or third line, or how a component behaves once its content genuinely wraps.
A list with a realistic item count, not three items
Three items is the default demo length and rarely stresses anything. Seven to ten items reveals whether the component scrolls, truncates, or just keeps growing without bound.
An image at the largest size your schema allows
Reveals whether max-width and aspect-ratio constraints actually hold, and whether a caption below an oversized image still reads correctly.
Two of the same component back to back
Two blockquotes in a row, two cards in a row with no divider. Reveals doubled margins between adjacent instances of the same component, a bug that a single isolated instance can never show.
A table with more columns than the viewport comfortably fits
Reveals whether the component actually has horizontal scroll handling, or whether it just breaks the page layout at narrow widths.
Inline formatting inside a heading or a label
A bold word or a link inside an H2, inside a button label, inside a table header. Reveals whether your typography rules were written assuming plain text everywhere.
Content in both light and dark mode
The same fixture, rendered under both themes. Catches contrast and border-visibility issues that only show up once, in whichever theme the developer happened to be using while building the component.
The component with every optional slot filled at once
Icon, badge, secondary action, footnote, all present simultaneously, not tested one at a time. Reveals whether the layout has actually been designed for the maximal case or just happens to work for whichever combination someone tried first.
Why teams usually stop at three
Writing twelve distinct content variations by hand for every component is genuinely tedious, which is the real reason most teams do not do it. The fix is not more discipline, it is generating the variations instead of typing them: configure a placeholder generator for short content, long content, adjacent headings, and a maximal list once, save each as a fixture, and reuse the same twelve fixtures across every component that takes similar content. The cost of building the checklist drops from "write this by hand for every component" to "paste one of twelve saved fixtures."
Where Storybook fits
If your design system uses Storybook, these fixtures become dedicated stories: ShortContent, LongContent, AdjacentHeadings, MaximalSlots. Chromatic or any other visual regression tool then catches spacing and overflow regressions automatically on every PR, instead of relying on someone remembering to manually check a four-line paragraph before merging.