test.js

module.exports = {
	env: {
		mocha: true,
	},
	rules: {
		// Allow test files to play more loosely with types.
		"@typescript-eslint/explicit-function-return-type": "off",

		// Allow non-null assertions in tests.
		"@typescript-eslint/no-non-null-assertion": "off",

		// Allow type aliases in tests.
		"@typescript-eslint/no-type-alias": "off",

		// Unit tests may need unbound method references for sinon.
		"@typescript-eslint/unbound-method": "off",

		// Test files may need to make stub classes, which don't need their own files.
		"max-classes-per-file": "off",

		// Allow test declarations to exceed max line length.
		"max-len": ["error", {
			code: 100,
			ignorePattern: "^\\s*(?:x?it|specify|describe|context)(?:\\.skip)?\\(",
		}],

		// Prevent `only` from being left on a test or test group.
		"no-restricted-properties": [
			"error",
			{object: "it", property: "only"},
			{object: "specify", property: "only"},
			{object: "describe", property: "only"},
			{object: "context", property: "only"},
		],

		// Synchronous methods are okay for test runs.
		"no-sync": "off",

		// Unit tests may need to access 'private' members.
		"no-underscore-dangle": "off",

		// Needed for chai, which implements some assertions as getters.
		"no-unused-expressions": 0,

		// Non-arrow callbacks are recommended by mocha docs.
		"prefer-arrow-callback": "off",
	},
};