Terratest Helm Charts Fails with Go Unit tests - unit-testing

Question

I'm trying to unit test my Helm charts using Terratest, but running into a strange error:
Here is my unit test:
package grafana
import (
"fmt"
"testing"
corev1 "k8s.io/api/core/v1"
"github.com/gruntwork-io/terratest/modules/helm"
)
func TestGrafanaHelmChartTemplate(t *testing.T) {
// Path to the helm chart we will test
helmChartGrafanaPath := "../../../open-electrons-monitoring"
// Setup the args. For this test, we will set the following input values:
// - image=grafana:latest
options := &helm.Options{
SetValues: map[string]string{"image": "grafana:latest"},
}
// Run RenderTemplate to render the template and capture the output.
output := helm.RenderTemplate(t, options, helmChartGrafanaPath, "pod", []string{"templates/grafana/grafana-deployment.yml"})
// Now we use kubernetes/client-go library to render the template output into the Pod struct. This will
// ensure the Pod resource is rendered correctly.
var pod corev1.Pod
helm.UnmarshalK8SYaml(t, output, &pod)
// Finally, we verify the pod spec is set to the expected container image value
expectedContainerImage := "grafana:latest"
podContainers := pod.Spec.Containers
fmt.Print(pod.Spec)
fmt.Print("*********************************************************")
if podContainers[0].Image != expectedContainerImage {
t.Fatalf("Rendered container image (%s) is not expected (%s)", podContainers[0].Image, expectedContainerImage)
}
}
Here is what the output of the deployment looks like:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: apiVersion: apps/v1
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: kind: Deployment
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: metadata:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: name: grafana-open-electrons-monitoring
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: namespace: open-electrons-monitoring-ns
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: labels:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: app.kubernetes.io/name: open-electrons-grafana
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: app.kubernetes.io/component: monitoring
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: app.kubernetes.io/part-of: open-electrons-grafana
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: app.kubernetes.io/managed-by: helm
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: app.kubernetes.io/instance: open-electrons-grafana
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: app.kubernetes.io/version: refs/tags/v0.0.11 # TODO: Better use the Grafana version
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: spec:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: replicas: 1
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: selector:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: matchLabels:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: app: open-electrons-grafana
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: strategy:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: rollingUpdate:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: maxSurge: 1
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: maxUnavailable: 1
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: type: RollingUpdate
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: template:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: metadata:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: creationTimestamp: null
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: labels:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: name: open-electrons-grafana
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: spec:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: securityContext:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: runAsUser: 1000
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: runAsGroup: 3000
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: fsGroup: 2000
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: runAsNonRoot: true
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: containers:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: - image: grafana/grafana:latest
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: imagePullPolicy: IfNotPresent
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: name: open-electrons-grafana
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: ports:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: - containerPort: 3000
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: protocol: TCP
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: resources:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: limits:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: memory: "1Gi"
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: cpu: "1000m"
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: requests:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: memory: 500M
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: cpu: "500m"
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: volumeMounts:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: - mountPath: /var/lib/grafana
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: name: grafana-storage
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: - mountPath: /etc/grafana/provisioning/datasources
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: name: grafana-datasources
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: readOnly: false
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: restartPolicy: Always
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: terminationGracePeriodSeconds: 30
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: volumes:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: - name: grafana-storage
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: emptyDir: {}
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: - name: grafana-datasources
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: configMap:
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: defaultMode: 420
TestGrafanaHelmChartTemplate 2023-02-12T18:59:01+01:00 logger.go:66: name: grafana-datasources
{[] [] [] [] <nil> <nil> map[] <nil> false false false <nil> nil [] nil [] [] <nil> nil [] <nil> <nil> <nil> map[] [] <nil>}*********************************************************--- FAIL: TestGrafanaHelmChartTemplate (0.06s)
Here is the output:
panic: runtime error: index out of range [0] with length 0 [recovered]
panic: runtime error: index out of range [0] with length 0
goroutine 5 [running]:
testing.tRunner.func1.2({0x1440620, 0xc0002a85b8})
/usr/local/go/src/testing/testing.go:1526 +0x24e
testing.tRunner.func1()
/usr/local/go/src/testing/testing.go:1529 +0x39f
panic({0x1440620, 0xc0002a85b8})
/usr/local/go/src/runtime/panic.go:884 +0x213
Why should this fail? What am I missing here?

Answer 1

I managed to get it fixed. The import should be like this:
appsv1 "k8s.io/api/apps/v1"
I then have to modify the instantiation of the Deployment object:
var deployment appsv1.Deployment
instead of the Pod object.