jest/prefer-lowercase-title

Jest prints a title after the titles of the blocks around it, as in cart › adds an item. A capital in the middle of that line reads like the start of a new sentence, and a mix of both styles is harder to scan.

--fix makes the first letter lowercase. Snapshots are stored under their test's title, so update them afterwards.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"jest/prefer-lowercase-title" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"jest/prefer-lowercase-title" = ["error", {
  ignore = [],
  allowedPrefixes = [], # list of strings
  ignoreTopLevelDescribe = false,
  lowercaseFirstCharacterOnly = true,
}]

Examples#

example.ts1 problem

import { expect, test } from "@jest/globals";

test("Adds an item", () => {
  expect(cart.add(item)).toBe(1);
});

example.tsNo problems

import { expect, test } from "@jest/globals";

test("adds an item", () => {
  expect(cart.add(item)).toBe(1);
});

Options#

Option	Default	What it does
`ignore`	`[]`	Functions to skip: `"describe"`, `"test"`, `"it"`. `"test"` doesn't cover `it`.
`allowedPrefixes`	`[]`	Allow a title that starts with one of these strings.
`ignoreTopLevelDescribe`	`false`	Allow a capital in a `describe` that isn't inside another block.
`lowercaseFirstCharacterOnly`	`true`	Set it to `false` to report an uppercase letter anywhere in the title. `--fix` then makes the whole title lowercase.

allowedPrefixes is for titles that start with a name you can't change:

example.tswith { "allowedPrefixes": ["GET", "POST"] }No problems

import { test } from "@jest/globals";

test("GET /users returns a list", () => {});

With ignoreTopLevelDescribe, you can name the outer describe after a class or a component. Only "Checkout" is reported here:

example.tswith { "ignoreTopLevelDescribe": true }1 problem

import { describe, test } from "@jest/globals";

describe("Cart", () => {
  describe("Checkout", () => {
    test("adds an item", () => {});
  });
});

With { "lowercaseFirstCharacterOnly": false }:

example.tswith { "lowercaseFirstCharacterOnly": false }1 problem

import { test } from "@jest/globals";

test("adds an Item", () => {});