update

• Type: boolean | 'new' | 'all' | 'none'
• Default: false
• CLI: -u, --update, --update=false, --update=new, --update=none

Define snapshot update behavior.

• true or 'all': updates all changed snapshots and deletes obsolete ones
• new: generates new snapshots without changing or deleting obsolete ones
• none: does not write snapshots and fails on snapshot mismatches, missing snapshots, and obsolete snapshots

When update is false (the default), Vitest resolves snapshot update mode by environment:

• Local runs (non-CI): works same as new
• CI runs (process.env.CI is truthy): works same as none