jestjs/jest · error · TypeError

Shard / requested, but test sequencer in has no shard…

Error message

Shard ${globalConfig.shard.shardIndex}/${globalConfig.shard.shardCount} requested, but test sequencer ${Sequencer.name} in ${globalConfig.testSequencer} has no shard method.

What it means

Thrown when the `--shard` CLI option (or `globalConfig.shard`) is used but the configured custom test sequencer class does not implement a `shard` method. Jest checks `typeof sequencer.shard !== 'function'` at runtime before attempting to call it, because sharding is an opt-in capability that custom sequencers must explicitly support.

Solutions

1. Add a `shard` method to your custom sequencer class, or remove the custom `testSequencer` from config to use the default sequencer which supports sharding.
2. If the custom sequencer is from a third-party package, upgrade it or check for a newer version that implements `shard`.
3. Remove the `--shard` flag from the CI command if sharding is not needed.

Example fix

// before: CustomSequencer.js
const Sequencer = require('@jest/test-sequencer').default;
class CustomSequencer extends Sequencer {
  sort(tests) { /* custom sort */ return tests; }
}

// after: add shard method
const Sequencer = require('@jest/test-sequencer').default;
class CustomSequencer extends Sequencer {
  sort(tests) { /* custom sort */ return tests; }
  shard(tests, { shardIndex, shardCount }) {
    const shardSize = Math.ceil(tests.length / shardCount);
    const shardStart = (shardIndex - 1) * shardSize;
    return tests.slice(shardStart, shardStart + shardSize);
  }
}

// Validate the custom sequencer supports sharding before running with --shard
const Sequencer = require('./CustomSequencer');
function validateSequencerShard(SequencerClass, hasShard) {
  if (hasShard && typeof SequencerClass.prototype.shard !== 'function') {
    throw new Error(`${SequencerClass.name} must implement shard(tests, options)`);
  }
}

function hasShardMethod(seq: unknown): seq is { shard(tests: unknown[], shard: {shardIndex: number; shardCount: number}): Promise<unknown[]> } {
  return typeof (seq as any)?.shard === 'function';
}

When it happens

Trigger: Running Jest with `--shard=1/4` (e.g. for CI parallelization) while `testSequencer` in the config points to a custom class that extends `@jest/test-sequencer` but does not define a `shard(tests, shardOptions)` method.

Common situations: Migrating from a non-sharded CI to a sharded one without updating a custom test sequencer. Using a third-party sequencer package that predates the sharding API. Adding `--shard` to CI scripts while a project-level custom sequencer is present.

Related errors

• Jest: Got error running
• The shard option / requires to be lower or equal than .
• The shard option requires 1-based values, received 0 or…
• The shard option requires a string in the format of
• Watch plugin configuration error

AI-assisted analysis of jestjs/jest@8e6d128e4a (2026-08-10). Data as JSON: /api/errors/71cc7082e6749ce9. Report an issue: GitHub.

Appendix: source

Thrown at packages/jest-core/src/runJest.ts:293

      const matches = await getTestPaths(
        globalConfig,
        context.config,
        searchSource,
        outputStream,
        changedFilesPromise && (await changedFilesPromise),
        jestHooks,
        filter,
      );
      allTests = [...allTests, ...matches.tests];

      return {context, matches};
    }),
  );
  performance.mark('jest/getTestPaths:end');

  if (globalConfig.shard) {
    if (typeof sequencer.shard !== 'function') {
      throw new TypeError(
        `Shard ${globalConfig.shard.shardIndex}/${globalConfig.shard.shardCount} requested, but test sequencer ${Sequencer.name} in ${globalConfig.testSequencer} has no shard method.`,
      );
    }
    allTests = await sequencer.shard(allTests, globalConfig.shard);
  }

  allTests = await sequencer.sort(allTests);

  if (globalConfig.onlyFailures) {
    if (failedTestsCache) {
      allTests = failedTestsCache.filterTests(allTests);
    } else {
      allTests = await sequencer.allFailedTests(allTests);
    }
  }

  if (globalConfig.listTests) {
    const testsPaths = [...new Set(allTests.map(test => test.path))];

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