> For the complete documentation index, see [llms.txt](https://argos-ci.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://argos-ci.com/docs/learn/how-to-guides/ci-pipelines/parallel-testing-sharding.md).

# Parallel testing (sharding)

Boost test suite efficiency with Argos Parallel Testing: Automate and streamline concurrent test executions across multiple environments effortlessly.

### Playwright

Argos seamlessly integrates with Playwright, offering out-of-the-box support for [Playwright tests sharding](https://playwright.dev/docs/test-sharding). This means zero configuration hassle for you. For more details, refer to the [Argos Playwright SDK](/docs/sdks-reference/playwright.md).

If you use an advanced orchestration system like the excellent one from [Currents](https://currents.dev/), use `argos finalize`.

### Other SDKs

For environments beyond Playwright, Argos facilitates sharding through two key environment variables, simplifying the setup:

* `ARGOS_PARALLEL`: Activate the parallel mode.
* `ARGOS_PARALLEL_TOTAL`: Specifies the number of parallel nodes. It's crucial to ensure equal calls to Argos upload across these nodes.
* `ARGOS_PARALLEL_INDEX`: Specifies the index of the current parallel node. Must start from `1`.
* `ARGOS_PARALLEL_NONCE`: A unique identifier for each build. In most CI environments, Argos will automatically generate this for you.

{% hint style="info" %}
Alternatively, use `--parallel`, `--parallel-nonce`, `--parallel-total` and `--parallel-index` flags with the CLI or `parallel: { nonce: string, total: number, index: number }` within SDK options.
{% endhint %}

### Modes

There is two parallel modes available:

* If `ARGOS_PARALLEL_TOTAL` is set to a `number`, Argos will wait for this number of upload before finalizing the build.
* If `ARGOS_PARALLEL_TOTAL` is set to `-1`, Argos will wait for a `argos finalize` call to finalize the build.

#### Implementing in GitHub Actions

**With a known number of shards**

Below is a practical example showcasing how to configure Argos sharding within a GitHub Actions workflow.

{% code title=".github/workflows/ci.yml" %}

```yml
jobs:
  e2e-tests:
    timeout-minutes: 60
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        shardIndex: [1, 2, 3, 4]
        shardTotal: [4]
    steps:
      # ---
      # Here you setup your repo and run your E2E tests
      # ---
      - name: Upload screenshots to Argos
        env:
          ARGOS_PARALLEL: true
          ARGOS_PARALLEL_TOTAL: ${{ matrix.shardTotal }}
          ARGOS_PARALLEL_INDEX: ${{ matrix.shardIndex }}
          # ARGOS_PARALLEL_NONCE is automatically detected

        run: npm exec -- argos upload ./screenshots
```

{% endcode %}

**With a finalize call**

Below is a practical example showcasing how to configure Argos sharding within a GitHub Actions workflow.

{% code title=".github/workflows/ci.yml" %}

```yml
jobs:
  e2e-tests:
    timeout-minutes: 60
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        shardIndex: [1, 2, 3, 4]
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
      - run: npm ci
      # ---
      # Here you setup your repo and run your E2E tests
      # ---
      - name: Upload screenshots to Argos
        env:
          ARGOS_PARALLEL: true
          ARGOS_PARALLEL_TOTAL: -1
          ARGOS_PARALLEL_INDEX: ${{ matrix.shardIndex }}
          # ARGOS_PARALLEL_NONCE is automatically detected

        run: npm exec -- argos upload ./screenshots

  finalize:
    timeout-minutes: 60
    runs-on: ubuntu-latest
    # Finalize the build even if some shards have failed
    if: ${{ always() }}
    needs: ["e2e-tests"]
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
      - run: npm ci
      - name: Finalize argos build
        env:
          # ARGOS_PARALLEL_NONCE is automatically detected

        run: npm exec -- argos finalize
```

{% endcode %}


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