jest/prefer-lowercase-title Style

What it does

Enforce it, test, describe, and bench to have descriptions that begin with a lowercase letter. This provides more readable test failures. This rule is not enabled by default.

Examples

Examples of incorrect code for this rule:

it("Adds 1 + 2 to equal 3", () => {
  expect(sum(1, 2)).toBe(3);
});

Examples of correct code for this rule:

it("adds 1 + 2 to equal 3", () => {
  expect(sum(1, 2)).toBe(3);
});

This rule is compatible with eslint-plugin-vitest, to use it, add the following configuration to your .oxlintrc.json:

{
  "rules": {
    "vitest/prefer-lowercase-title": "error"
  }
}

Configuration

This rule accepts a configuration object with the following properties:

allowedPrefixes

type: string[]

default: []

This array option allows specifying prefixes, which contain capitals that titles can start with. This can be useful when writing tests for API endpoints, where you'd like to prefix with the HTTP method. By default, nothing is allowed (the equivalent of { "allowedPrefixes": [] }).

Example of correct code for the { "allowedPrefixes": ["GET"] } option:

/* jest/prefer-lowercase-title: ["error", { "allowedPrefixes": ["GET"] }] */
describe("GET /live");

ignore

type: string[]

default: []

This array option controls which Jest or Vitest functions are checked by this rule. There are four possible values:

• "describe"
• "test"
• "it"
• "bench"

By default, none of these options are enabled (the equivalent of { "ignore": [] }).

Example of correct code for the { "ignore": ["describe"] } option:

/* jest/prefer-lowercase-title: ["error", { "ignore": ["describe"] }] */
describe("Uppercase description");

Example of correct code for the { "ignore": ["test"] } option:

/* jest/prefer-lowercase-title: ["error", { "ignore": ["test"] }] */
test("Uppercase description");

Example of correct code for the { "ignore": ["it"] } option:

/* jest/prefer-lowercase-title: ["error", { "ignore": ["it"] }] */
it("Uppercase description");

ignoreTopLevelDescribe

type: boolean

default: false

This option can be set to allow only the top-level describe blocks to have a title starting with an upper-case letter.

Example of correct code for the { "ignoreTopLevelDescribe": true } option:

/* jest/prefer-lowercase-title: ["error", { "ignoreTopLevelDescribe": true }] */
describe("MyClass", () => {
  describe("#myMethod", () => {
    it("does things", () => {
      //
    });
  });
});

lowercaseFirstCharacterOnly

type: boolean

default: true

This option can be set to only validate that the first character of a test name is lowercased.

Example of correct code for the { "lowercaseFirstCharacterOnly": true } option:

/* vitest/prefer-lowercase-title: ["error", { "lowercaseFirstCharacterOnly": true }] */
describe("myClass", () => {
  describe("myMethod", () => {
    it("does things", () => {
      //
    });
  });
});

Example of incorrect code for the { "lowercaseFirstCharacterOnly": true } option:

/* vitest/prefer-lowercase-title: ["error", { "lowercaseFirstCharacterOnly": true }] */
describe("MyClass", () => {
  describe("MyMethod", () => {
    it("does things", () => {
      //
    });
  });
});

How to use

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

Config (.oxlintrc.json)

{
  "plugins": ["jest"],
  "rules": {
    "jest/prefer-lowercase-title": "error"
  }
}

CLI

oxlint --deny jest/prefer-lowercase-title --jest-plugin

References

• Rule Source