oxc-project/oxc · warning

This argument should be a number.

Error message

This argument should be a number.

What it means

From the oxlint `prefer-expect-assertions` rule family: even when `expect.assertions()` receives exactly one argument, that argument must be a numeric literal (Jest compares the executed-assertion count to it). This companion diagnostic fires on the argument itself when it is not a number — strings, identifiers, or expressions make the declared count unverifiable or wrong at runtime.

Source

Thrown at crates/oxc_linter/src/rules/shared/jest_vitest/prefer_expect_assertions.rs:180

    )
    .with_help("Rename the parameter to avoid shadowing the global `expect`.")
    .with_label(span)
}

pub fn has_assertions_takes_no_arguments(span: Span, prefix: &str) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("`{prefix}.hasAssertions` expects no arguments."))
        .with_help(format!("Remove the arguments from `{prefix}.hasAssertions()`."))
        .with_label(span)
}

fn assertions_requires_one_argument(span: Span, prefix: &str) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("`{prefix}.assertions` expects a single argument of type number."))
        .with_help(format!("Pass a single numeric argument to `{prefix}.assertions()`."))
        .with_label(span)
}

fn assertions_requires_number_argument(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("This argument should be a number.")
        .with_help("Replace this argument with a numeric literal.")
        .with_label(span)
}

pub fn resolve_expect_local_name(ctx: &LintContext<'_>, sources: &[&str]) -> CompactStr {
    for entry in &ctx.module_record().import_entries {
        if entry.is_type {
            continue;
        }

        let source = entry.module_request.name();
        if !sources.contains(&source) {
            continue;
        }

        let crate::module_record::ImportImportName::Name(import_name) = &entry.import_name else {
            continue;
        };

View on GitHub (pinned to e1e7af627c)

Solutions

1. Replace the argument with a plain numeric literal after counting the assertions.
2. If the count is genuinely dynamic, drop `expect.assertions` and use `expect.hasAssertions()`.
3. Restructure the test so the number of assertions is static (e.g. unroll a loop of assertions).

Example fix

// before
it('runs each case', () => {
  expect.assertions(cases.length);
  for (const c of cases) expect(run(c)).toBe(true);
});

// after
it.each(cases)('runs %j', (c) => {
  expect(run(c)).toBe(true);
});

// .oxlintrc.json
{ "rules": { "jest/prefer-expect-assertions": "error" } }

npx oxlint tests/

When it happens

Trigger: `expect.assertions('2')`, `expect.assertions(count)` (identifier), `expect.assertions(n * 2)` — an assertions() call with one argument whose expression is not a numeric literal.

Common situations: Dynamic test generation where the count is computed; passing a string digit from config; variables pulled from a fixtures table.

Related errors

• `{prefix}.hasAssertions` expects no arguments.
• `{prefix}.assertions` expects a single argument of type numb
• `expect` must be inside of a test block.
• Suggest using `toBeCalledWith()` or `toHaveBeenCalledWith()`
• Suggest using the built-in equality matchers.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/5b5cb0c07bac9597. Report an issue: GitHub.