bun:test/max-expects

A test with many assertions usually checks several things at once. The first expect that fails stops the test and hides any failures after it, and the test's name no longer tells you what broke.

By default a test can have 5 expect() calls. Each call after that is reported.

Configure

Off by default. To turn it on:

[lint.rules]
"bun:test/max-expects" = "error" # or "warn"

Every option, set to its default:

[lint.rules]
"bun:test/max-expects" = ["error", {
  max = 5,
}]

Examples

Reported:

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

test("creates a user", () => {
  const user = createUser({ name: "Ada", email: "ada@example.com" });
  expect(user.id).toBeGreaterThan(0);
  expect(user.name).toBe("Ada");
  expect(user.email).toBe("ada@example.com");
  expect(user.role).toBe("member");
  expect(user.active).toBe(true);
  expect(user.createdAt).toBeInstanceOf(Date);
});

Not reported:

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

test("keeps the name and the email", () => {
  const user = createUser({ name: "Ada", email: "ada@example.com" });
  expect(user).toMatchObject({ name: "Ada", email: "ada@example.com" });
});

test("fills in the defaults", () => {
  const user = createUser({ name: "Ada", email: "ada@example.com" });
  expect(user.id).toBeGreaterThan(0);
  expect(user.role).toBe("member");
  expect(user.active).toBe(true);
  expect(user.createdAt).toBeInstanceOf(Date);
});

Options

[lint.rules]
"bun:test/max-expects" = ["error", { max = 2 }]

With max = 2, the third call is reported:

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

test("parses a URL", () => {
  const url = parse("https://example.com:8080/docs");
  expect(url.host).toBe("example.com");
  expect(url.port).toBe(8080);
  expect(url.path).toBe("/docs");
});

An expect in a loop, an if or a callback counts toward the test around it:

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

test("lists active users", () => {
  const users = listUsers({ active: true });
  expect(users).toHaveLength(2);
  expect(users[0].name).toBe("Ada");
  for (const user of users) {
    expect(user.active).toBe(true);
  }
});

A helper function gets its own count. expect.assertions() and expect.hasAssertions() aren't counted.