eslint-plugin-hollow-tests

Catches tests that pass without checking anything.

// ❌ no assertion at all
it("saves the record", async () => {
  await save(record);
});

// ❌ assertions only inside a branch — nothing runs when the condition is false
it("uses the button when present", () => {
  if (hasButton) {
    expect(getButton()).toBeVisible();
  }
});

Both pass type checking and linting, and both raise the test count, so the code looks covered. Neither is something a reader reliably notices.

How this differs from expect-expect

vitest/expect-expect and jest/expect-expect check whether a test body contains a call to an assertion function. This rule goes two steps further.

| | expect-expect | hollow-tests | | ---- | ---- | ---- | | Body with no assertion | reported | reported | | Assertions only inside a branch | missed | reported | | Assertions moved into a helper | needs the helper listed in config | followed automatically within the file |

"Inside a branch" covers if, the conditional operator, the right-hand side of && and ||, a switch case, and catch. The test of an if always evaluates, so it counts as outside.

Install

npm install -D eslint-plugin-hollow-tests

// eslint.config.js
import hollowTests from "eslint-plugin-hollow-tests";

export default [
  {
    files: ["**/*.test.ts", "**/*.spec.ts", "e2e/**/*.ts"],
    plugins: { "hollow-tests": hollowTests },
    rules: { "hollow-tests/no-hollow-test": "error" },
  },
];

A ready-made config is also exported. Apply it to test files only.

import { recommended } from "eslint-plugin-hollow-tests";

export default [{ ...recommended, files: ["**/*.test.ts"] }];

Options

"hollow-tests/no-hollow-test": ["error", {
  assertionNames: ["expect", "assert"],
  testNames: ["it", "test"],
  optOutComment: "hollow-test-ok",
}]

| Option | Default | Meaning | | ---- | ---- | ---- | | assertionNames | ["expect", "assert"] | Calls that count as assertions. Member forms such as assert.equal(...) count too | | testNames | ["it", "test"] | Calls that introduce a test body. Modifiers (.skip, .each, …) are matched automatically | | optOutComment | "hollow-test-ok" | A test carrying a comment with this text is left alone |

Opting out

When there is a reason not to assert, write the reason next to it.

// hollow-test-ok only checks that rendering does not throw
it("does not throw", () => {
  render(<App />);
});

What it does not report

• Hooks. A call shaped like test.beforeEach is not treated as a test body. The modifiers are listed explicitly rather than matched with .*
• Expression bodies. () => expect(a).toBe(1) always runs
• Helpers from another file. Assertions are followed within a single file only. For a shared helper, add its name to assertionNames

License

MIT