@crescware/eslint-plugin-crescware-no-inline-expected

An oxlint JS plugin that forbids passing an inline object or array literal as the expected value to an expect(...) matcher. Declare the expected value in a const variable first.

Rule: no-inline-expected

When the expected value of an assertion is written inline as an object or array literal (expect(actual).toEqual({ ... }) / expect(actual).toStrictEqual([ ... ])), extract it into a named variable. A named expected separates "what is being compared" from "what the answer should be", keeps the assertion line short, and gives the expected value a name to refer to.

// NG: an inline object literal as the expected value
expect(actual).toEqual({ id: 1, name: "Alice" });

// NG: an inline array literal as the expected value
expect(actual).toEqual([1, 2, 3]);

// NG: an empty literal is still an inline literal
expect(actual).toEqual({});
expect(actual).toEqual([]);

// OK: the expected value is declared first
const expected = { id: 1, name: "Alice" };
expect(actual).toEqual(expected);

// OK: a non-literal argument is out of scope
expect(actual).toEqual(buildExpected());

By default the rule also enforces that, inside a test / it callback, the expected variable is declared first — at the top of the callback. Only declarations of variables that the expected value uses may precede it, and even those may not be part of the value passed to expect(...).

// NG: an unrelated variable is declared above expected
test("...", () => {
  const something = {};
  const expected = {};
  expect(something).toEqual(expected);
});

// NG: expected is aliased from the value under test
test("...", () => {
  const actual = { a: 1 };
  const expected = actual;
  expect(actual).toStrictEqual(expected);
});

// OK: expected is declared first
test("...", () => {
  const expected = {};
  const actual = {};
  expect(actual).toEqual(expected);
});

// OK: a variable used to build expected may precede it, as long as it is not
// the value under test
test("...", () => {
  const id = makeId();
  const expected = { id, name: "alice" };
  const actual = makeUser(id);
  expect(actual).toEqual(expected);
});

Scope

The rule fires when all of the following hold for a call expression:

• The callee is a member access whose property is one of the configured matchers (default: toEqual, toStrictEqual).
• The receiver chain is anchored at an expect(...) call. Modifier chains are followed, so expect(x).not.toEqual(...), expect(x).resolves.toEqual(...), expect(x).rejects.toEqual(...), and expect.soft(x).toEqual(...) are all in scope. An unrelated foo.toEqual({ ... }) that is not anchored at expect is not reported.
• An argument is a plain object literal (ObjectExpression) or array literal (ArrayExpression), optionally wrapped in as / satisfies clauses ({ ... } as Foo, [ ... ] as const, { ... } satisfies T, including multi-step chains such as { ... } as unknown as T). The wrappers are unwrapped to classify the underlying literal.

Notes:

• Object and array literals are treated the same, including empty {} / [].
• Every argument is inspected, so multi-argument matchers (e.g. a configured toHaveBeenCalledWith) report each inline literal.
• The rule applies to JavaScript (.js / .mjs / .cjs / .jsx) as well as TypeScript: it targets a runtime assertion call, not any TypeScript-only syntax.
• The expected-first check (on by default) only applies inside a test / it callback, and only when the expected value is a plain identifier declared directly in that callback. An expected value that is an inline literal, a call, or declared elsewhere (an outer scope, a parameter, an import) has no callback-top position to enforce and is left alone. Modifier and table forms (it.only, test.each(table)(...)) are recognized.
• Type-only declarations (type / interface) introduce no runtime value, so they are always allowed above the expected declaration, whether or not the expected value uses them.
• The rule does not autofix; it reports only.

Options

"crescware-no-inline-expected/no-inline-expected": [
  "error",
  {
    // The matcher names to check. Replaces the default set, not extends it.
    "matchers": ["toEqual", "toStrictEqual"],

    // true (default): inside a `test` / `it` callback the expected variable
    // must be declared first. Set to false to disable this check.
    "requireExpectedFirstInTest": true
  }
]

| Option | Type | Default | Effect | | ---------------------------- | ---------- | ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | matchers | string[] | ["toEqual", "toStrictEqual"] | The matcher names whose inline-literal arguments are reported. Setting this replaces the default set. Add names such as toMatchObject, toContainEqual, or toHaveBeenCalledWith to widen coverage. | | requireExpectedFirstInTest | boolean | true | When true, additionally requires the expected variable to be declared first inside its test / it callback. Only declarations of variables the expected value uses may precede it (and not the value under test). Set to false to disable this check. |

Usage

Register the plugin in your .oxlintrc.json and enable the rule:

{
  "jsPlugins": ["@crescware/eslint-plugin-crescware-no-inline-expected"],
  "rules": {
    "crescware-no-inline-expected/no-inline-expected": "error"
  }
}

Stack

• Runtime: Node.js 24 (via mise)
• Package manager: pnpm (via corepack)
• Language: TypeScript (native preview)
• Test: Vitest
• Lint: oxlint
• Format: oxfmt
• Unused code: Knip

Setup

mise install
corepack enable
pnpm install

Scripts

| Command | Description | | ------------------ | ---------------------------------------- | | pnpm build | Compile src to dist | | pnpm check | Run all checks (types, lint, knip, test) | | pnpm check:types | Type check | | pnpm check:lint | Lint and format check | | pnpm check:knip | Unused files/exports check | | pnpm test | Run fixture integration tests | | pnpm format | Fix lint and format |