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vitest/prefer-to-be-falsy Style

💡 A suggestion is available for this rule.

What it does

This rule warns when toBe(false) is used with expect or expectTypeOf. With --fix-suggestions, it will be replaced with toBeFalsy().

Why is this bad?

When testing for falsiness, toBeFalsy() expresses that intent directly. Unlike toBe(false), it also accepts non-boolean falsy values such as 0, null, and undefined. The replacement is a suggestion because it changes which values pass the assertion.

Examples

Examples of incorrect code for this rule:

expect(foo).toBe(false);
expectTypeOf(foo).toBe(false);

Examples of correct code for this rule:

expect(foo).toBeFalsy();
expectTypeOf(foo).toBeFalsy();

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
  "plugins": ["vitest"],
  "rules": {
    "vitest/prefer-to-be-falsy": "error"
  }
}

Config (oxlint.config.ts)

import { defineConfig } from "oxlint";

export default defineConfig({
  plugins: ["vitest"],
  rules: {
    "vitest/prefer-to-be-falsy": "error",
  },
});

CLI

oxlint --deny vitest/prefer-to-be-falsy --vitest-plugin

Version

This rule was added in v0.7.1.

References

• Rule Source
• Upstream rule docs
• Open rule in Oxc Playground