---
source: crates/biome_js_analyze/tests/spec_tests.rs
expression: Button.jsx
---
# Input
```jsx
// should generate diagnostics

export function Button() {
	return <button className="btn-invalid">This class does not exist</button>;
}

```

# Diagnostics
```
Button.jsx:4:28 lint/nursery/noUndeclaredStyles ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  i The CSS class btn-invalid is not defined in any imported stylesheet.
  
    3 │ export function Button() {
  > 4 │ 	return <button className="btn-invalid">This class does not exist</button>;
      │ 	                          ^^^^^^^^^^^
    5 │ }
    6 │ 
  
  i Referencing undefined classes often indicates a typo or a missing stylesheet, and will result in elements not being styled as intended.
  
  i Checked import tree:
    
    Button.jsx (this file)
      └─ imported by:
        ├─ • Block.jsx
        │ └─ imported by:
        │   └─ • Page.jsx
        │     └─ imported by:
        │       └─ • App.jsx -> which imports app.css
        └─ • Page.jsx
          └─ imported by:
            └─ • App.jsx -> which imports app.css
  
  
  i Either import a CSS file that defines this class or remove this class name.
  
  i This rule is still being actively worked on, so it may be missing features or have rough edges. Visit https://github.com/biomejs/biome/issues/9156 for more information or to report possible bugs.
  
  i This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  

```