bun:test/no-large-snapshots

Nobody reads a several-hundred-line snapshot in a review. When it changes, people update it without looking, and then the test passes no matter what the code does. A short snapshot, or an assertion on the few values that matter, still tells you something when it fails.

The rule counts the lines of the snapshot in toMatchInlineSnapshot and toThrowErrorMatchingInlineSnapshot. The limit is 50 lines. Snapshots in .snap files aren't checked.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"bun:test/no-large-snapshots" = "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/no-large-snapshots" = ["error", {
  # inlineMaxSize = <number>,
  maxSize = 50,
}]

Examples#

These examples set inlineMaxSize to 3 to stay short.

example.tswith { "inlineMaxSize": 3 }1 problem

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

test("loads the user", () => {
  expect(loadUser(1)).toMatchInlineSnapshot(`
    {
      "email": "ada@example.com",
      "id": 1,
      "name": "Ada",
    }
  `);
});

example.tswith { "inlineMaxSize": 3 }1 problem

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

test("creates a user", () => {
  expect(createUser("Ada")).toMatchInlineSnapshot({ id: expect.any(Number) }, `
    {
      "email": null,
      "id": Any<Number>,
      "name": "Ada",
    }
  `);
});

example.tswith { "inlineMaxSize": 3 }No problems

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

test("loads the user", () => {
  const user = loadUser(1);
  expect(user.name).toBe("Ada");
  expect(user.email).toMatchInlineSnapshot(`"ada@example.com"`);
});

Options#

Option	Default	What it does
`inlineMaxSize`	the value of `maxSize`	The most lines an inline snapshot can have.
`maxSize`	`50`	The limit to use when `inlineMaxSize` isn't set.

bunfig.toml

[lint.rules]
"bun:test/no-large-snapshots" = ["error", { inlineMaxSize = 20 }]

Without inlineMaxSize, maxSize applies:

example.tswith { "maxSize": 3 }1 problem

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

test("lists the roles", () => {
  expect(roles()).toMatchInlineSnapshot(`
    [
      "admin",
      "editor",
      "viewer",
    ]
  `);
});