How do I actively test my code while developing

[awalvie]

Currently following the CronJob tutorial from the kubebuilder book. I was stepping through https://book.kubebuilder.io/cronjob-tutorial/controller-implementation and realized that if I was on my own, writing the reconciliation logic from scratch I would have no idea what functions/structs/methods to make use of.

To give an analogy -- say I'm working on the backend of a webserver. I create a new route that gets the input from a form and writes it to a database. Here's how I would go about implementing said route:

• Create a route that does nothing
• Access the route -- ensure its hitting my function
• Print out the contents of the object I'm receiving in the function to figure out what structs/objects my incoming data is
• Write the unmarshal logic
• Access the route -- verify unmarshalling logic by printing out my unmarshaled struct
• Write the logic to push to database
  ...

you get the idea. There's an active feedback loop in the above workflow so that there's no guesswork involved. In the same way say if I was implementing the reconciliation logic on my own here's how I would start:

• Run the controller(?)
• Try to hit the Reconcile() function and print out the contexts of the request
• Write the logic for getting all the CronJobs
• Reload controller -- see the output

so on and so forth. Are there any docs that highlight what this process is like, if not, any ideas on how I could do this?

[camilamacedo86]

Hi @awalvie,

Overview

To validate your controller logic, you can use ENVTEST. Check out the examples under the controllers to create the suite and the test for each controller here. Note that you should have a test for each controller.

Additionally, you can perform end-to-end (e2e) tests to check your solution, with an example available under the testdata here. When creating a project with the Kubebuilder CLI, an initial scaffold is provided in test/e2e for your e2e tests. You can also refer to suite_test.go for using envtest.

If you use the Deploy Image plugin (more information here), it generates the scaffold to deploy and manage an image, including an implemented test. See this example here.

The Kubebuilder docs provide a section on writing tests with examples here.

Remember that following up the Operator Pattern, we declare the desired state and loop (reconcile) until it is ensured. It's recommended to re-trigger the reconciliation based on events raised, like updates, deletions, or creations of a Custom Resource that you are watching. Therefore, you can use kubectl, for example, to apply the CR and check the logs to know what is happening.

💡 Check the code generated by the Deploy Image plugin to understand Conditional Status and best practices. Review the Kubernetes API conventions here. The implementation can be seen in the code generated by the Deploy Image plugin here.

Also, use the e2e tests implemented in Kubebuilder as a reference, available here.

Iterative Development Process

For an iterative development process in Kubebuilder:

• Initial Setup: Start with a basic Reconcile function that logs its invocation.

  func (r *CronJobReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
      log.Printf("Reconciling CronJob: %s", req.NamespacedName)
      // Your code here
      return ctrl.Result{}, nil
  }

Testing and Logging

• Run the controller and trigger the Reconcile function by making changes to your Kubernetes objects (like CronJob).
• Use logging to understand the context and request data you receive in the Reconcile function.

Iterative Development

• Implement small logic parts, such as listing all CronJobs.
• Verify your code with logging.
• Gradually add more logic, for instance, processing each CronJob, handling errors, and updating the status.

Feedback Loop

• Test each new logic addition by re-running the controller.
• Use Kubernetes tools like kubectl to modify objects and observe your controller's reaction.
• Adjust your code based on the output and behavior you observe.

Additional Tips

• For ENVTEST tests, run make test to execute them. You can configure it to run against an existing cluster and use tools like kind for local testing.
• Consider setting up GitHub Actions with e2e tests and the make test target to ensure changes are validated when pushing PRs.
• Debugging tests can be done with tools like GolangIDEA.

I am closing this as sorted out, but feel free to reopen it if needed, or open new discussion topics for more specific questions after reviewing all the content and examples shared.

[awalvie]

Thank you so much for such a detailed response. Really appreciate it. Cheers!