Molecule Command Examples (with examples)

Molecule is a tool that helps in testing Ansible roles. It simplifies the process of creating and testing infrastructure code. In this article, we will explore and provide code examples for various use cases of the molecule command.

1: Creating a new Ansible role

To create a new Ansible role using Molecule, we can use the following command:

molecule init role --role-name role_name

Motivation: Creating a new Ansible role is the first step in writing infrastructure code. Molecule automates the process of setting up a testing environment for the role.

Explanation:

• molecule init initializes a new Molecule project.
• role specifies that we want to create an Ansible role.
• --role-name is an optional argument that allows us to specify the name of the role.

Example output:

INFO     Initializing new role role_name...

2: Running tests

To run tests for an Ansible role using Molecule, we can use the following command:

molecule test

Motivation: Testing is an essential part of writing infrastructure code. Molecule simplifies the process of running tests and ensures that the role behaves as expected.

Explanation:

• molecule test executes the test sequence defined in the molecule.yml file.
• The test sequence typically includes tasks like creating instances, configuring them, and running tests.

Example output:

INFO     Performing test sequence...

3: Starting the instance

To start an instance for testing an Ansible role using Molecule, we can use the following command:

molecule create

Motivation: Before running tests on an Ansible role, we need to create an instance to test on. Molecule automates this process and ensures that the instance is set up correctly.

Explanation:

• molecule create creates a new instance as defined in the molecule.yml file.
• The instance can be a virtual machine or a container.

Example output:

INFO     Starting instance...

4: Configuring the instance

To configure an instance for testing an Ansible role using Molecule, we can use the following command:

molecule converge

Motivation: Once the instance is created, we need to configure it with the necessary dependencies and prerequisites for the role. Molecule automates this process and ensures that the instance is properly configured.

Explanation:

• molecule converge configures the instance using the playbook defined in the molecule.yml file.
• The playbook installs the required packages and performs any other necessary configuration steps.

Example output:

INFO     Configuring instance...

5: Listing scenarios of the instance

To list the scenarios of an instance for testing an Ansible role using Molecule, we can use the following command:

molecule matrix converge

Motivation: An instance can have multiple scenarios, each representing a different testing scenario or configuration. Listing the available scenarios helps us understand the different configuration options we can test.

Explanation:

• molecule matrix lists the available scenarios for the instance.
• converge is an action that tells Molecule to show the scenarios.

Example output:

INFO     Showing available scenarios...
Scenario 1: default
Scenario 2: scenario1

6: Logging into the instance

To log in to an instance for testing an Ansible role using Molecule, we can use the following command:

molecule login

Motivation: Logging into the instance allows us to debug and troubleshoot any issues during the testing process. It provides an interactive shell session on the instance.

Explanation:

• molecule login logs into the instance defined in the molecule.yml file.
• This command uses the default login method configured for the instance (SSH, Docker exec, etc.).

Example output:

INFO     Logging into instance...

In this article, we explored different use cases of the molecule command with code examples. We learned how to create a new Ansible role, run tests, start and configure instances, list available scenarios, and log into the instance. Molecule simplifies the testing process and ensures the reliability of Ansible roles.