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Writing controller tests

Testing Kubernetes controllers is a big subject, and the boilerplate testing files generated for you by kubebuilder are fairly minimal.

To walk you through integration testing patterns for Kubebuilder-generated controllers, we will revisit the CronJob we built in our first tutorial and write a simple test for it.

The basic approach is that, in your generated suite_test.go file, you will use envtest to create a local Kubernetes API server, instantiate and run your controllers, and then write additional *_test.go files to test it using Ginko.

If you want to tinker with how your envtest cluster is configured, see section Configuring envtest for integration tests as well as the envtest docs.

Test Environment Setup

../../cronjob-tutorial/testdata/project/controllers/suite_test.go

When we created the CronJob API with kubebuilder create api in a previous chapter, Kubebuilder already did some test work for you. Kubebuilder scaffolded a controllers/suite_test.go file that does the bare bones of setting up a test environment.

First, it will contain the necessary imports.

Apache License

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Imports
package controllers

import (
	"path/filepath"
	"testing"

	. "github.com/onsi/ginkgo"
	. "github.com/onsi/gomega"
	"k8s.io/client-go/kubernetes/scheme"
	"k8s.io/client-go/rest"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/envtest"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/log/zap"

	batchv1 "tutorial.kubebuilder.io/project/api/v1"
	// +kubebuilder:scaffold:imports
)

// These tests use Ginkgo (BDD-style Go testing framework). Refer to
// http://onsi.github.io/ginkgo/ to learn more about Ginkgo.

Now, let’s go through the code generated.

var cfg *rest.Config
var k8sClient client.Client // You'll be using this client in your tests.
var testEnv *envtest.Environment

var _ = BeforeSuite(func(done Done) {
	logf.SetLogger(zap.LoggerTo(GinkgoWriter, true))

First, the envtest cluster is configured to read CRDs from the CRD directory Kubebuilder scaffolds for you.

	By("bootstrapping test environment")
	testEnv = &envtest.Environment{
		CRDDirectoryPaths: []string{filepath.Join("..", "config", "crd", "bases")},
	}

Then, we start the envtest cluster.

	var err error
	cfg, err = testEnv.Start()
	Expect(err).ToNot(HaveOccurred())
	Expect(cfg).ToNot(BeNil())

The autogenerated test code will add the CronJob Kind schema to the default client-go k8s scheme. This ensures that the CronJob API/Kind will be used in our test controller.

	err = batchv1.AddToScheme(scheme.Scheme)
	Expect(err).NotTo(HaveOccurred())

After the schemas, you will see the following marker. This marker is what allows new schemas to be added here automatically when a new API is added to the project.

	// +kubebuilder:scaffold:scheme

A client is created for our test CRUD operations.

	k8sClient, err = client.New(cfg, client.Options{Scheme: scheme.Scheme})
	Expect(err).ToNot(HaveOccurred())
	Expect(k8sClient).ToNot(BeNil())

One thing that this autogenerated file is missing, however, is a way to actually start your controller. The code above will set up a client for interacting with your custom Kind, but will not be able to test your controller behavior. If you want to test your custom controller logic, you’ll need to add some familiar-looking manager logic to your BeforeSuite() function, so you can register your custom controller to run on this test cluster.

You may notice that the code below runs your controller with nearly identical logic to your CronJob project’s main.go! The only difference is that the manager is started in a separate goroutine so it does not block the cleanup of envtest when you’re done running your tests.

Once you’ve added the code below, you can actually delete the k8sClient above, because you can get k8sClient from the manager (as shown below).

	k8sManager, err := ctrl.NewManager(cfg, ctrl.Options{
		Scheme: scheme.Scheme,
	})
	Expect(err).ToNot(HaveOccurred())

	err = (&CronJobReconciler{
		Client: k8sManager.GetClient(),
		Log:    ctrl.Log.WithName("controllers").WithName("CronJob"),
	}).SetupWithManager(k8sManager)
	Expect(err).ToNot(HaveOccurred())

	go func() {
		err = k8sManager.Start(ctrl.SetupSignalHandler())
		Expect(err).ToNot(HaveOccurred())
	}()

	k8sClient = k8sManager.GetClient()
	Expect(k8sClient).ToNot(BeNil())

	close(done)
}, 60)

Kubebuilder also generates boilerplate functions for cleaning up envtest and actually running your test files in your controllers/ directory. You won’t need to touch these.

var _ = AfterSuite(func() {
	By("tearing down the test environment")
	err := testEnv.Stop()
	Expect(err).ToNot(HaveOccurred())
})

func TestAPIs(t *testing.T) {
	RegisterFailHandler(Fail)

	RunSpecsWithDefaultAndCustomReporters(t,
		"Controller Suite",
		[]Reporter{envtest.NewlineReporter{}})
}

Now that you have your controller running on a test cluster and a client ready to perform operations on your CronJob, we can start writing integration tests!

Testing your Controller’s Behavior

../../cronjob-tutorial/testdata/project/controllers/cronjob_controller_test.go

Ideally, we should have one <kind>_conroller_test.go for each controller scaffolded and called in the test_suite.go. So, let’s write our example test for the CronJob controller (cronjob_controller_test.go.)

Apache License

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Imports

As usual, we start with the necessary imports. We also define some utility variables.

package controllers

import (
	"context"
	"reflect"
	"time"

	. "github.com/onsi/ginkgo"
	. "github.com/onsi/gomega"
	batchv1 "k8s.io/api/batch/v1"
	batchv1beta1 "k8s.io/api/batch/v1beta1"
	v1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"

	cronjobv1 "tutorial.kubebuilder.io/project/api/v1"
)

The first step to writing a simple integration test is to actually create an instance of CronJob you can run tests against. Note that to create a CronJob, you’ll need to create a stub CronJob struct that contains your CronJob’s specifications.

Note that when we create a stub CronJob, the CronJob also needs stubs of its required downstream objects. Without the stubbed Job template spec and the Pod template spec below, the Kubernetes API will not be able to create the CronJob.

var _ = Describe("CronJob controller", func() {

	// Define utility constants for object names and testing timeouts/durations and intervals.
	const (
		CronjobName      = "test-cronjob"
		CronjobNamespace = "test-cronjob-namespace"
		JobName          = "test-job"

		timeout  = time.Second * 10
		duration = time.Second * 10
		interval = time.Millisecond * 250
	)

	Context("When updating CronJob Status", func() {
		It("Should increase CronJob Status.Active count when new Jobs are created", func() {
			By("By creating a new CronJob")
			ctx := context.Background()
			cronJob := &cronjobv1.CronJob{
				TypeMeta: metav1.TypeMeta{
					APIVersion: "batch.tutorial.kubebuilder.io/v1",
					Kind:       "CronJob",
				},
				ObjectMeta: metav1.ObjectMeta{
					Name:      CronjobName,
					Namespace: CronjobNamespace,
				},
				Spec: cronjobv1.CronJobSpec{
					Schedule: "1 * * * *",
					JobTemplate: batchv1beta1.JobTemplateSpec{
						Spec: batchv1.JobSpec{
							// For simplicity, we only fill out the required fields.
							Template: v1.PodTemplateSpec{
								Spec: v1.PodSpec{
									// For simplicity, we only fill out the required fields.
									Containers: []v1.Container{
										{
											Name:  "test-container",
											Image: "test-image",
										},
									},
									RestartPolicy: v1.RestartPolicyOnFailure,
								},
							},
						},
					},
				},
			}
			Expect(k8sClient.Create(ctx, cronJob)).Should(Succeed())

		

After creating this CronJob, let’s check that the CronJob’s Spec fields match what we passed in. Note that, because the k8s apiserver may not have finished creating a CronJob after our Create() call from earlier, we will use Gomega’s Eventually() testing function instead of Expect() to give the apiserver an opportunity to finish creating our CronJob.

Eventually() will repeatedly run the function provided as an argument every interval seconds until (a) the function’s output matches what’s expected in the subsequent Should() call, or (b) the number of attempts * interval period exceed the provided timeout value.

In the examples below, timeout and interval are Go Duration values of our choosing.

			cronjobLookupKey := types.NamespacedName{Name: CronjobName, Namespace: CronjobNamespace}
			createdCronjob := &cronjobv1.CronJob{}

			// We'll need to retry getting this newly created CronJob, given that creation may not immediately happen.
			Eventually(func() bool {
				err := k8sClient.Get(ctx, cronjobLookupKey, createdCronjob)
				if err != nil {
					return false
				}
				return true
			}, timeout, interval).Should(BeTrue())
			// Let's make sure our Schedule string value was properly converted/handled.
			Expect(createdCronjob.Spec.Schedule).Should(Equal("1 * * * *"))
		

Now that we’ve created a CronJob in our test cluster, the next step is to write a test that actually tests our CronJob controller’s behavior. Let’s test the CronJob controller’s logic responsible for updating CronJob.Status.Active with actively running jobs. We’ll verify that when a CronJob has a single active downstream Job, its CronJob.Status.Active field contains a reference to this Job.

First, we should get the test CronJob we created earlier, and verify that it currently does not have any active jobs. We use Gomega’s Consistently() check here to ensure that the active job count remains 0 over a duration of time.

			By("By checking the CronJob has zero active Jobs")
			Consistently(func() (int, error) {
				err := k8sClient.Get(ctx, cronjobLookupKey, createdCronjob)
				if err != nil {
					return -1, err
				}
				return len(createdCronjob.Status.Active), nil
			}, duration, interval).Should(Equal(0))
		

Next, we actually create a stubbed Job that will belong to our CronJob, as well as its downstream template specs. We set the Job’s status’s “Active” count to 2 to simulate the Job running two pods, which means the Job is actively running.

We then take the stubbed Job and set its owner reference to point to our test CronJob. This ensures that the test Job belongs to, and is tracked by, our test CronJob. Once that’s done, we create our new Job instance.

			By("By creating a new Job")
			testJob := &batchv1.Job{
				ObjectMeta: metav1.ObjectMeta{
					Name:      JobName,
					Namespace: CronjobNamespace,
				},
				Spec: batchv1.JobSpec{
					Template: v1.PodTemplateSpec{
						Spec: v1.PodSpec{
							// For simplicity, we only fill out the required fields.
							Containers: []v1.Container{
								{
									Name:  "test-container",
									Image: "test-image",
								},
							},
							RestartPolicy: v1.RestartPolicyOnFailure,
						},
					},
				},
				Status: batchv1.JobStatus{
					Active: 2,
				},
			}

			// Note that your CronJob’s GroupVersionKind is required to set up this owner reference.
			kind := reflect.TypeOf(cronjobv1.CronJob{}).Name()
			gvk := cronjobv1.GroupVersion.WithKind(kind)

			controllerRef := metav1.NewControllerRef(createdCronjob, gvk)
			testJob.SetOwnerReferences([]metav1.OwnerReference{*controllerRef})
			Expect(k8sClient.Create(ctx, testJob)).Should(Succeed())
		

Adding this Job to our test CronJob should trigger our controller’s reconciler logic. After that, we can write a test that evaluates whether our controller eventually updates our CronJob’s Status field as expected!

			By("By checking that the CronJob has one active Job")
			Eventually(func() ([]string, error) {
				err := k8sClient.Get(ctx, cronjobLookupKey, createdCronjob)
				if err != nil {
					return nil, err
				}

				names := []string{}
				for _, job := range createdCronjob.Status.Active {
					names = append(names, job.Name)
				}
				return names, nil
			}, timeout, interval).Should(ConsistOf(JobName), "should list our active job %s in the active jobs list in status", JobName)
		})
	})

})

After writing all this code, you can run go test ./... in your controllers/ directory again to run your new test!

This Status update example above demonstrates a general testing strategy for a custom Kind with downstream objects. By this point, you hopefully have learned the following methods for testing your controller behavior:

  • Setting up your controller to run on an envtest cluster
  • Writing stubs for creating test objects
  • Isolating changes to an object to test specific controller behavior

Advanced Examples

There are more involved examples of using envtest to rigorously test controller behavior. Examples include:

  • Azure Databricks Operator: see their fully fleshed-out suite_test.go as well as any *_test.go file in that directory like this one.