jestjs/jest · error · Error

Tests cannot be nested. Test

Error message

Tests cannot be nested. Test "${spec.description}" cannot run because it is nested within "${currentSpec.description}".

What it means

Jasmine builds the test tree during the describe phase, then executes specs. Calling `it(...)` inside another spec's body (an `it` callback) means the nested spec is created DURING execution, when `currentSpec` is already set — jasmine cannot run it and would silently skip it. Env.it detects `currentSpec !== null` at line 584 and throws this Error naming both the nested and the outer spec to make the misuse explicit.

Solutions

Move the nested `it` out to the describe level so it is a sibling, not a child of the other spec.
For dynamic case generation, use `describe.each` or generate the cases inside a `describe` (not an `it`).
If you need sub-assertions inside a test, use multiple `expect()` calls rather than nested `it`.

Example fix

// before — nested it, throws at runtime
it('outer', () => {
  it('inner', () => { expect(1).toBe(1); });
});
// after — siblings
describe('outer', () => {
  it('inner', () => { expect(1).toBe(1); });
});

Defensive patterns

Strategy: validation

Validate before calling

// Static lint: forbid it() calls inside it() bodies.
// Use eslint-plugin-jest rule: 'no-nested-tests' or a custom visitor
// that errors when an `it`/`test` CallExpression appears inside another
// `it`/`test` CallExpression's callback.

Prevention

Register tests at the describe level, never inside an it body.
Use describe.each or it.each for data-driven cases rather than loops in specs.
Add an ESLint rule (eslint-plugin-jest) to catch nested test definitions.

When it happens

Trigger: Writing `it('outer', () => { it('inner', () => {}) })`. The check `currentSpec !== null` at Env.ts:584 is true because the outer spec is executing. The error includes both `spec.description` (inner) and `currentSpec.description` (outer).

Common situations: Coming from Mocha which historically allowed (then deprecated) nested tests; a helper that registers specs and is accidentally called from within a spec body rather than a describe body; a loop inside a spec that tries to generate cases dynamically.

Related errors

AI-assisted analysis of jestjs/jest@8e6d128e4a (2026-08-10). Data as JSON: /api/errors/fdf135df1aa18f03. Report an issue: GitHub.

Appendix: source

Thrown at packages/jest-jasmine2/src/jasmine/Env.ts:585

        if (typeof fn !== 'function') {
          throw new TypeError(
            `Invalid second argument, ${fn}. It must be a callback function.`,
          );
        }
        const spec = specFactory(
          description,
          fn,
          currentDeclarationSuite,
          timeout,
        );
        if (currentDeclarationSuite.markedPending) {
          spec.pend();
        }

        // When a test is defined inside another, jasmine will not run it.
        // This check throws an error to warn the user about the edge-case.
        if (currentSpec !== null) {
          throw new Error(
            `Tests cannot be nested. Test "${spec.description}" cannot run because it is nested within "${currentSpec.description}".`,
          );
        }
        currentDeclarationSuite.addChild(spec);
        return spec;
      };

      this.xit = function (...args) {
        const spec = this.it.apply(this, args);
        spec.pend('Temporarily disabled with xit');
        return spec;
      };

      this.todo = function () {
        const description = arguments[0];
        if (arguments.length !== 1 || typeof description !== 'string') {
          throw new ErrorWithStack(
            'Todo must be called with only a description.',

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