#prefer-ending-with-an-expect

#Configuration

import { defineConfig, rstestPlugin } from '@rslint/core';

export default defineConfig([
  rstestPlugin.configs.recommended,
  {
    rules: {
      'rstest/prefer-ending-with-an-expect': 'error',
    },
  },
]);

#Rule Details

Require the last statement a test case runs to be an assertion. A test that ends by calling into the code under test, changing state, or awaiting a promise has exercised something without checking the result, which is usually an unfinished test rather than a deliberate one. Only the final statement is examined; assertions earlier in the body do not satisfy the rule.

A block body contributes its last statement, an arrow function written without braces contributes its expression, and a leading await is looked through. expect, expect.soft, expect.poll, and Chai's assert all count as assertions, including when they reach the call site through the test context, a namespace import, a destructured fixture, or a renamed import. assert is recognized through every one of those except the test context, which Rstest does not use to provide it. Additional asserting functions can be configured with assertFunctionNames.

Chai asserts through property getters as well as calls, so a test ending in expect(cart).to.be.empty or context.expect(ok).to.be.true satisfies the rule. A chain that resolves no matcher still does not: expect(cart).not stops on a modifier and expect(cart).toBe never invokes its matcher, and neither asserts anything.

A destructured key is read when it names a constant, so const { ['expect']: check } = import.meta.rstest is recognized exactly like const { expect: check }. A key computed from a value that is only known at runtime, such as const { [key]: check } = import.meta.rstest, names no API the rule can identify; a test whose last statement asserts through such a binding is reported even though it does assert. Bind the API under a readable key to avoid this.

Both Rstest call shapes are recognized — test(name, fn, timeout) and test(name, options, fn) — so a case that passes its options object second is checked like any other. test.todo is exempt because the function it is given never runs, and a callback passed by reference rather than written inline is left alone. The rule recognizes Rstest globals and APIs imported from @rstest/core, rstack/test, and @rstest/playwright, including aliases, namespace and CommonJS imports, import.meta.rstest, parameterized cases such as test.each and test.for, chained modifiers such as test.concurrent, and fixture-extended test APIs built with test.extend. Foreign test frameworks, locally shadowed names, and type-only bindings are ignored. Type information is not required.

#Incorrect

import { expect, test } from '@rstest/core';

test('lets me change the selected option', () => {
  const container = render(MySelect, { selected: 1 });

  expect(container.toHTML()).toContain('value="1" selected');

  container.setProp('selected', 2);
});

#Correct

import { expect, test } from '@rstest/core';

test('lets me change the selected option', () => {
  const container = render(MySelect, { selected: 1 });

  expect(container.toHTML()).toContain('value="1" selected');

  container.setProp('selected', 2);

  expect(container.toHTML()).toContain('value="2" selected');
});

#Options

{
  "rstest/prefer-ending-with-an-expect": [
    "error",
    {
      "assertFunctionNames": ["expect", "assert", "expectSaga"],
      "additionalTestBlockFunctions": ["scenario"]
    }
  ]
}