jest/no-conditional-expect Correctness

✅ This rule is turned on by default.

What it does

This rule prevents the use of expect in conditional blocks, such as ifs & catch(s). This includes using expect in callbacks to functions named catch, which are assumed to be promises.

Why is this bad?

Jest only considers a test to have failed if it throws an error, meaning if calls to assertion functions like expect occur in conditional code such as a catch statement, tests can end up passing but not actually test anything. Additionally, conditionals tend to make tests more brittle and complex, as they increase the amount of mental thinking needed to understand what is actually being tested.

Examples

Examples of incorrect code for this rule:

it("foo", () => {
  doTest && expect(1).toBe(2);
});

it("bar", () => {
  if (!skipTest) {
    expect(1).toEqual(2);
  }
});

it("baz", async () => {
  try {
    await foo();
  } catch (err) {
    expect(err).toMatchObject({ code: "MODULE_NOT_FOUND" });
  }
});

it("throws an error", async () => {
  await foo().catch((error) => expect(error).toBeInstanceOf(error));
});

Examples of correct code for this rule:

it("foo", () => {
  expect(!value).toBe(false);
});

function getValue() {
  if (process.env.FAIL) {
    return 1;
  }
  return 2;
}

it("foo", () => {
  expect(getValue()).toBe(2);
});

it("validates the request", () => {
  try {
    processRequest(request);
  } catch {
  } finally {
    expect(validRequest).toHaveBeenCalledWith(request);
  }
});

it("throws an error", async () => {
  await expect(foo).rejects.toThrow(Error);
});

How to use

To enable this rule in the CLI or using the config file, you can use:

CLI

oxlint --deny jest/no-conditional-expect --jest-plugin

Config (.oxlintrc.json)

{
  "plugins": ["jest"],
  "rules": {
    "jest/no-conditional-expect": "error"
  }
}

References

• Rule Source