test: add tests for reduceToClassName()

[layershifter]

See title.

[github-actions[bot]]

📊 Bundle size report

Unchanged fixtures

| Package & Exports | Size (minified/GZIP) | | -------------------------------------------------------------------------------------------------------------------------- | --------------------------: | | core
\_\_resetStyles (makeResetStyles) | `273 B`
`197 B` | | core
\_\_styles (makeStyles) | `1.662 kB`
`793 B` | | core
makeResetStyles (runtime) | `17.14 kB`
`6.569 kB` | | core
makeStyles (runtime) | `21.651 kB`
`8.202 kB` | | core
mergeClasses | `1.821 kB`
`876 B` | | core
shorthands.padding() | `4.781 kB`
`1.537 kB` | | react
\_\_css | `1.658 kB`
`774 B` | | react
\_\_styles | `3.776 kB`
`1.668 kB` | | react
makeResetStyles (runtime) | `19.285 kB`
`7.429 kB` | | react
makeStaticStyles (runtime) | `9.225 kB`
`4.051 kB` | | react
makeStyles (runtime) | `23.803 kB`
`9.044 kB` | | shadow-dom
createShadowDOMRenderer | `3.468 kB`
`1.467 kB` |

_{🤖 This report was generated against 50e95e9f78354deda53ba23113ce2ee608021eb0}