What is Ansible Molecule?

Using Ansible Molecule for testing your roles


As an experienced DevOps and Automation architect, I have come across numerous technologies that streamline the deployment and management of infrastructure. One such tool that stands out is Ansible Molecule, which brings automation and testing to the forefront of infrastructure development. In this blog, we will explore the various aspects of Ansible Molecule and its practical applications.

What is Ansible Molecule?

Ansible Molecule is an open-source framework that provides support for testing and development of Ansible roles. It allows developers to validate the functionality and configuration of their infrastructure code in a consistent and reproducible manner. Molecule integrates seamlessly with popular testing frameworks, making it an essential tool for DevOps teams.

Examples of Using Ansible Molecule

To understand how Ansible Molecule can be utilized, let's take a look at a couple of examples.

  1. Testing Infrastructure Code: With Molecule, you can create test scenarios to validate the behavior of your Ansible roles. For instance, you can simulate the deployment of a web server and verify its functionality using automated tests.

  2. Continuous Integration and Delivery: Molecule can be integrated with Continuous Integration (CI) systems like Jenkins, allowing you to automatically test your infrastructure code whenever changes are made. This ensures that any modifications to your Ansible roles are thoroughly validated before deployment.

Components of Ansible Molecule

Ansible Molecule consists of several key components that enhance its functionality:

  1. Scenario: A scenario defines the target environment and the set of actions that should be performed during testing. It specifies the platforms, provisioners, and verifier to be used.

  2. Driver: Molecule supports multiple drivers, such as Docker, Vagrant, and EC2, which provide the necessary infrastructure to run the tests. These drivers enable easy creation of isolated test environments.

  3. Provisioner: The provisioner is responsible for preparing the test environment by installing dependencies and configuring the system. Ansible is commonly used as a provisioner in Molecule.

  4. Verifier: Verifiers validate the state of the system after running the Ansible playbook. They ensure that the desired outcome is achieved and that the infrastructure code is functioning as expected.

Use Cases for Ansible Molecule

Ansible Molecule can be used in various scenarios, including:

  1. Role Development: Molecule facilitates the development and testing of Ansible roles, allowing you to iterate quickly and ensure the reliability of your infrastructure code.

  2. Integration Testing: By using Molecule, you can perform integration testing of your infrastructure code against different platforms and configurations. This helps identify any compatibility issues early on.

  3. Continuous Deployment: Molecule can be integrated into your CI/CD pipeline, enabling automated testing and deployment of infrastructure code. This ensures that your deployments are predictable and reliable.

Limitations and When Not to Use Ansible Molecule

While Molecule is a powerful tool, it may not be suitable for every use case. Some limitations include:

  1. Complex Deployments: If your infrastructure has complex multi-node deployments or requires specialized hardware, Molecule may not be the best fit.

  2. Limited Platform Support: Molecule supports a wide range of platforms, but it may not cover all possible target environments. In such cases, manual testing or alternative tools may be necessary.

Best Practices with Ansible Molecule

To make the most of Ansible Molecule, consider the following best practices:

  1. Keep Tests Isolated: Ensure that each test scenario is isolated from others to prevent interference and maintain reproducibility.

  2. Leverage Verifiers: Use appropriate verifiers to validate the desired state of your infrastructure code. This helps catch any configuration drift or unexpected changes.

  3. Automate Testing: Integrate Molecule with your CI/CD pipeline to automate the testing and validation of your infrastructure code.

Pros and Cons of Ansible Molecule

Here are some pros and cons to consider when using Ansible Molecule:


  • Simplifies the development and testing of Ansible roles

  • Enables integration testing across different platforms and configurations

  • Supports multiple provisioners and verifiers for flexibility

  • Integrates well with CI/CD pipelines for automated testing and deployment


  • May not be suitable for complex deployments or specialized hardware

  • Limited platform support compared to manual testing

  • Requires additional setup and configuration for effective use

Alternatives to Ansible Molecule

While Ansible Molecule is a popular tool, there are alternative frameworks available for testing and development of infrastructure code. Some notable alternatives include:

  • Test Kitchen: Test Kitchen is a testing framework that supports multiple provisioning and verification tools. It is widely used in the Chef community but can also be used with Ansible.

  • InSpec: InSpec is an open-source testing framework that focuses on verifying compliance and security requirements. It can be used alongside Ansible for comprehensive infrastructure testing.

Summary and Conclusion

Ansible Molecule is a powerful tool that enhances the development and testing of Ansible roles. It provides a consistent and reproducible way to validate infrastructure code, ensuring the reliability and functionality of deployments. By leveraging Molecule in conjunction with other DevOps practices, such as CI/CD pipelines, you can achieve robust and automated infrastructure management.

In this blog, we explored the concept of Ansible Molecule, its components, use cases, limitations, best practices, and alternatives. Armed with this knowledge, you can now confidently incorporate Ansible Molecule into your DevOps toolkit.

Happy testing and automation!

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