feat: support update: "none" and add docs about CI behavior

hi-ogawa · hi-ogawa · commit 004e264cfee0 · 2026-02-20T11:48:59.000+09:00
diff --git a/docs/config/update.md b/docs/config/update.md
@@ -5,11 +5,17 @@ outline: deep
 
 # update <CRoot /> {#update}
 
-- **Type:** `boolean | 'new' | 'all'`
+- **Type:** `boolean | 'new' | 'all' | 'none'`
 - **Default:** `false`
-- **CLI:** `-u`, `--update`, `--update=false`, `--update=new`
+- **CLI:** `-u`, `--update`, `--update=false`, `--update=new`, `--update=none`
 
-Update snapshot files. The behaviour depends on the value:
+Define snapshot update behavior.
 
-- `true` or `'all'`: updates all changed snapshots and delete obsolete ones
+- `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`
diff --git a/docs/guide/cli-generated.md b/docs/guide/cli-generated.md
@@ -16,7 +16,7 @@ Path to config file
 - **CLI:** `-u, --update [type]`
 - **Config:** [update](/config/update)
 
-Update snapshot (accepts boolean, "new" or "all")
+Update snapshot (accepts boolean, "new", "all" or "none")
 
 ### watch
 
diff --git a/docs/guide/snapshot.md b/docs/guide/snapshot.md
@@ -79,6 +79,12 @@ Or you can use the `--update` or `-u` flag in the CLI to make Vitest update snap
 vitest -u
 ```
 
+### CI behavior
+
+By default, Vitest does not write snapshots in CI (`process.env.CI` is truthy) and any snapshot mismatches, missing snapshots, and obsolete snapshots fail the run. See [`update`](/config/update) for the details.
+
+An **obsolete snapshot** is a snapshot entry (or snapshot file) that no longer matches any collected test. This usually happens after removing or renaming tests.
+
 ## File Snapshots
 
 When calling `toMatchSnapshot()`, we store all snapshots in a formatted snap file. That means we need to escape some characters (namely the double-quote `"` and backtick `` ` ``) in the snapshot string. Meanwhile, you might lose the syntax highlighting for the snapshot content (if they are in some language).
diff --git a/examples/basic/test/suite.test.ts b/examples/basic/test/suite.test.ts
@@ -7,6 +7,7 @@ describe('suite name', () => {
 
   it('bar', () => {
     expect(1 + 1).eq(2)
+    expect(3).toMatchInlineSnapshot()
   })
 
   it('snapshot', () => {
diff --git a/packages/vitest/src/node/cli/cli-config.ts b/packages/vitest/src/node/cli/cli-config.ts
@@ -84,7 +84,7 @@ export const cliOptionsConfig: VitestCLIOptions = {
   },
   update: {
     shorthand: 'u',
-    description: 'Update snapshot (accepts boolean, "new" or "all")',
+    description: 'Update snapshot (accepts boolean, "new", "all" or "none")',
     argument: '[type]',
   },
   watch: {
diff --git a/packages/vitest/src/node/config/resolveConfig.ts b/packages/vitest/src/node/config/resolveConfig.ts
@@ -566,7 +566,7 @@ export function resolveConfig(
     expand: resolved.expandSnapshotDiff ?? false,
     snapshotFormat: resolved.snapshotFormat || {},
     updateSnapshot:
-      UPDATE_SNAPSHOT === 'all' || UPDATE_SNAPSHOT === 'new'
+      UPDATE_SNAPSHOT === 'all' || UPDATE_SNAPSHOT === 'new' || UPDATE_SNAPSHOT === 'none'
         ? UPDATE_SNAPSHOT
         : isCI && !UPDATE_SNAPSHOT ? 'none' : UPDATE_SNAPSHOT ? 'all' : 'new',
     resolveSnapshotPath: options.resolveSnapshotPath,
diff --git a/packages/vitest/src/node/types/config.ts b/packages/vitest/src/node/types/config.ts
@@ -380,7 +380,7 @@ export interface InlineConfig {
    *
    * @default false
    */
-  update?: boolean | 'all' | 'new'
+  update?: boolean | 'all' | 'new' | 'none'
 
   /**
    * Watch mode

Original file line number	Diff line number	Diff line change
`@@ -380,7 +380,7 @@ export interface InlineConfig {`
`380`	`380`	`*`
`381`	`381`	`* @default false`
`382`	`382`	`*/`
`383`		`- update?: boolean \| 'all' \| 'new'`
	`383`	`+ update?: boolean \| 'all' \| 'new' \| 'none'`
`384`	`384`
`385`	`385`	`/**`
`386`	`386`	`* Watch mode`