bun:test/prefer-ending-with-an-expect

Anything a test does after its last assertion isn't checked. If the test ends with a click, a request or a save, that step can do the wrong thing and the test still passes.

The test's last statement must be a call to expect, with or without await. A test with an empty body is reported. So is one that ends with an if, a loop or a return, even if there's an expect inside.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"bun:test/prefer-ending-with-an-expect" = "error" # or "warn"

Every option, set to its default. The ones that are commented out are unset by default.

bunfig.toml

[lint.rules]
"bun:test/prefer-ending-with-an-expect" = ["error", {
  # assertFunctionNames = <list of strings>,
  additionalTestBlockFunctions = [], # list of strings
}]

Examples#

example.ts1 problem

import { expect, test } from "bun:test";

test("renames the user", async () => {
  const user = await createUser("Ada");
  expect(user.name).toBe("Ada");
  await user.rename("Grace");
});

example.ts1 problem

import { expect, test } from "bun:test";

test("loads the user", () => {
  return expect(loadUser(1)).resolves.toBeDefined();
});

example.tsNo problems

import { expect, test } from "bun:test";

test("renames the user", async () => {
  const user = await createUser("Ada");
  await user.rename("Grace");
  expect(user.name).toBe("Grace");
});

test("loads the user", async () => {
  await expect(loadUser(1)).resolves.toBeDefined();
});

Options#

Option	Default	What it does
`assertFunctionNames`	any name that contains `expect`	The calls that count as an assertion, besides `expect` itself.
`additionalTestBlockFunctions`	`[]`	Other functions to check like `test`, such as your own wrappers around it or a hook like `afterEach`.

By default, a helper or a method with expect in its name counts:

example.tsNo problems

import { test } from "bun:test";

test("has a valid user", () => {
  expectValidUser(loadUser(1));
});

test("responds with 200", async () => {
  await request(app).get("/users").expect(200);
});

With assertFunctionNames, only expect and the names in the list count. A name can be a dotted path. * matches any characters in one part of the path, and ** matches any number of parts, including none.

example.tswith { "assertFunctionNames": ["assert*", "request.**.expect"] }No problems

import { test } from "bun:test";

test("has a valid user", () => {
  assertValidUser(loadUser(1));
});

test("responds with 200", async () => {
  await request(app).get("/users").expect(200);
});

example.tswith { "assertFunctionNames": ["assert*"] }1 problem

import { test } from "bun:test";

test("has a valid user", () => {
  expectValidUser(loadUser(1));
});

With additionalTestBlockFunctions, your own wrapper or a hook is checked too:

example.tswith { "additionalTestBlockFunctions": ["scenario"] }1 problem

import { expect } from "bun:test";
import { scenario } from "./helpers";

scenario("saves the user", async () => {
  expect(await saveUser()).toBe(true);
  await cleanup();
});

example.tswith { "additionalTestBlockFunctions": ["afterEach"] }1 problem

import { afterEach, expect } from "bun:test";

afterEach(() => {
  expect(liveSockets()).toBe(0);
  resetDatabase();
});