no-disabled-vitest-isolation

Disallow test.isolate: false in Vitest configuration.

Rule catalog ID: R020

Targeted pattern scope

• vitest.config.*
• vitest.workspace.*
• vite.config.* when a Vitest test block is used
• root and inline project test.isolate

What this rule reports

This rule reports explicit test.isolate: false assignments.

Why this rule exists

Vitest defaults isolate to true to keep test files separated. Turning isolation off can leak runtime state between files and make failures order-dependent.

This plugin targets robust Vite/Vitest configuration guardrails, so flagging committed disabled-isolation config is a high-signal safety check.

❌ Incorrect

import { defineConfig } from "vitest/config";

export default defineConfig({
    test: {
        isolate: false,
    },
});

✅ Correct

import { defineConfig } from "vitest/config";

export default defineConfig({
    test: {
        isolate: true,
    },
});

Behavior and migration notes

• this rule only reports explicit false assignments
• it does not require setting isolate when omitted
• if you intentionally disable isolation for a specific local workflow, prefer temporary CLI or local-only overrides instead of committing the setting globally

ESLint flat config example

import vite from "@typpi/eslint-plugin-vite";

export default [vite.configs.strict, vite.configs.vitest];

When not to use it

Disable this rule only if your suite intentionally relies on shared global state between files and you accept increased flake risk.

Package documentation

• Vitest config reference
• Vitest isolate option

Further reading

• no-unsafe-vitest-flags
• no-zero-vitest-timeout