vitest/max-expects

Enforce a maximum number of expect() calls in a test

A test with many assertions usually checks several things at once. The first expect that fails stops the test, so it hides the failures after it, and the test's name no longer says 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:

bunfig.toml
[lint.rules]
"vitest/max-expects" = "error" # or "warn"

Every option, set to its default:

bunfig.toml
[lint.rules]
"vitest/max-expects" = ["error", {
  max = 5,
}]

Examples#

example.ts1 problem
import { expect, test } from "vitest";

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);
});
example.tsNo problems
import { expect, test } from "vitest";

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#

OptionDefaultWhat it does
max5The number of expect() calls allowed.
bunfig.toml
[lint.rules]
"vitest/max-expects" = ["error", { max = 2 }]

With max = 2, the third call is reported:

example.tswith { "max": 2 }1 problem
import { expect, test } from "vitest";

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");
});

Calls are counted per function and per block. An expect inside a loop or a callback doesn't count toward the test around it, so this isn't reported:

example.tswith { "max": 2 }No problems
import { expect, test } from "vitest";

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);
  }
});