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no-constant-assertions

Disallow assertions whose subject is a static constant.

Rule detailsโ€‹

Assertions should prove behavior from the code under test. An assertion that starts from a literal, static object, static array, or other constant expression can pass without executing any product code. These checks often come from temporary matcher experiments, copy/paste mistakes, or tests that were scaffolded but never connected to the real subject.

Incorrectโ€‹

it("passes without exercising code", () => {
    expect(true).toBe(true);
});
it("checks only a static fixture", () => {
    expect({ enabled: true, id: "abc" }).toEqual({
        enabled: true,
        id: "abc",
    });
});

Correctโ€‹

it("returns an enabled user", () => {
    expect(loadUser("abc")).toEqual({
        enabled: true,
        id: "abc",
    });
});
it("returns an admin role", () => {
    expect(createRoles()).toContain("admin");
});

What this rule reportsโ€‹

This rule reports executable it(...) and test(...) callbacks when an expect(...) assertion receives a static subject such as:

  • a literal: expect(true).toBe(true)
  • a no-substitution template: expect(`ready`).toBe("ready")
  • a static object or array: expect({ ok: true }).toEqual({ ok: true })
  • a wrapped static value: expect("ready" as const).toMatch(/^ready$/u)

toBeTruthy() and toBeFalsy() are left to no-weak-truthy-assertions, so projects do not receive duplicate reports for the same assertion.

Optionsโ€‹

This rule has no options.

When not to use itโ€‹

Disable this rule for tests that intentionally document matcher behavior, JavaScript runtime constants, or compatibility quirks. Product and library tests should assert values produced by the code under test.

Rule catalog ID: R015