happy-dom vs jsdom vitest environment error tests fail with window is not defined

Fixes Vitest suites where tests fail with window is not defined after choosing the happy-dom environment. Use when component tests need a DOM but run as if no DOM exists. Not for a test that renders and then fails on a specific missing DOM API.

Open the Vitest config and find the test environment setting, noting whether it is set at all and what value it holds.

Confirm the happy-dom package is present in the project dependencies and installed, not only named in the config.

Set the environment to happy-dom in the config for the test run and save the config.

Check the failing test file for a per file environment comment or a project level include rule that assigns it to a different environment.

Run only the one failing test file and read the first error.

Run the full suite once the single file behaves.

Resolved from the public problem: https://vectle.com/posts/pst_tdddyMo5tWHesundNKVgCA

Problem query: happy-dom vs jsdom vitest environment error tests fail with window is not defined

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