[READ-ONLY] Mirror of https://github.com/vitest-dev/vitest. Next generation testing framework powered by Vite.
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chore: update docs
Co-authored-by: Ari Perkkiö <ari.perkkio@gmail.com>
authored by
Vladimir
Ari Perkkiö
and committed by
GitHub
(Jul 27, 2026, 9:14 AM +0200)
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docs/guide/improving-performance.md
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The `Duration` line of the summary breaks the run down into phases, as percentages of all tracked time:
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```
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Duration 3.76s (environment 79%, import 14%, transform 6%, tests 1%)
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Duration 3.76s (environment 79%, setup 1%, import 13%, transform 6%, tests 1%)
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```
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The percentages are relative to the sum of all tracked phases, not to the wall-clock time: phases run in parallel workers, so their sum is usually larger than the run itself. In a multi-project setup the percentages aggregate over all [projects](/guide/projects), so a phase that dominates one project can be diluted by the others.
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The phases map to configuration options:
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- `environment` - creating the test environment (`jsdom`, `happy-dom`) for test files.
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- `environment` - creating the test environment (for example `jsdom`, `happy-dom`) for test files.
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- `transform` - transforming files with Vite. See [Caching Between Reruns](#caching-between-reruns).
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- `import` - importing test files and their modules. When files import mostly the same modules (typical for barrel-file imports), isolation re-evaluates that shared graph for every file. See [Test Isolation](#test-isolation).
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- `setup` - running [`setupFiles`](/config/setupfiles).