add integration test guide

Author: crimsonfaith91

e2e.md renamed to docs/testing/e2e.md

@@ -0,0 +1,80 @@
+**Writing and Running Integration Tests**
+
+This article explores steps to write and run integration tests for Kubebuilder. Kubebuilder provides a template for writing integration tests. You can simply run all integration (and unit) tests within the project by running: `make test`
+
+For example, there is a controller watches *Parent* objects. The *Parent* objects create *Child* objects. Note that the *Child* objects must have their `.ownerReferences` field setting to the `Parent` objects. You can find the template under `pkg/controller/parent/parent_controller_test.go`:
+```
+package parent
+
+import (
+	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
+	childapis "k8s.io/child/pkg/apis"
+	childv1alpha1 "k8s.io/childrepo/pkg/apis/child/v1alpha1"
+	parentapis "k8s.io/parent/pkg/apis"
+	parentv1alpha1 "k8s.io/parentrepo/pkg/apis/parent/v1alpha1"
+	
+	...<other import items>...
+)
+
+const timeout = time.Second * 5
+
+var c client.Client
+var expectedRequest = reconcile.Request{NamespacedName: types.NamespacedName{Name: "parent", Namespace: "default"}}
+var childKey = types.NamespacedName{Name: "child", Namespace: "default"}
+
+func TestReconcile(t *testing.T) {
+	g := gomega.NewGomegaWithT(t)
+
+	// Parent instance to be created.
+	parent := &parentv1alpha1.Parent{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "parent",
+			Namespace: "default",
+		},
+		Spec: metav1.ParentSpec{
+			SomeSpecField:    "SomeSpecValue",
+			AnotherSpecField: "AnotherSpecValue",
+		},
+	}
+
+	// Setup the Manager and Controller. Wrap the Controller Reconcile function
+	// so it writes each request to a channel when it is finished.
+	mgr, err := manager.New(cfg, manager.Options{})
+
+	// Setup Scheme for all resources.
+	if err = parentapis.AddToScheme(mgr.GetScheme()); err != nil {
+		t.Logf("failed to add Parent scheme: %v", err)
+	}
+	if err = childapis.AddToScheme(mgr.GetScheme()); err != nil {
+		t.Logf("failed to add Child scheme: %v", err)
+	}
+
+	// Set up and start test manager.
+	reconciler, err := newReconciler(mgr)
+	g.Expect(err).NotTo(gomega.HaveOccurred())
+	recFn, requests := SetupTestReconcile(reconciler)
+	g.Expect(add(mgr, recFn)).NotTo(gomega.HaveOccurred())
+	defer close(StartTestManager(mgr, g))
+
+	// Create the Parent object and expect the Reconcile and Child to be created.
+	c = mgr.GetClient()
+	err = c.Create(context.TODO(), parent)
+	g.Expect(err).NotTo(gomega.HaveOccurred())
+	defer c.Delete(context.TODO(), parent)
+	g.Eventually(requests, timeout).Should(gomega.Receive(gomega.Equal(expectedRequest)))
+
+	// Verify Child is created.
+	child := &childv1alpha1.Child{}
+	g.Eventually(func() error { return c.Get(context.TODO(), childKey, child) }, timeout).
+		Should(gomega.Succeed())
+
+	// Manually delete Child since GC isn't enabled in the test control plane.
+	g.Expect(c.Delete(context.TODO(), child)).To(gomega.Succeed())
+}
+```
+
+`SetupTestReconcile` function above brings up an API server and etcd instance. Note that there is no any node creation for integration testing environment. If you want to test your controller on a real node, you should write end-to-end tests.
+
+The manager is started as part of the test itself (`StartTestManager` function).
+
+Both functions are located in `pkg/controller/parent/parent_controller_suite_test.go` file. The file also contains a `TestMain` function that allows you to specify CRD directory paths for the testing environment.