Add TestCoreDNSDaemonSetReconciliation

Add an end-to-end test that verifies that the operator reconciles changes
to the dns-default daemonset.  This new test adds a node selector to the
daemonset and verifies that the operator reverts the change.

The operator already has unit tests to verify that the daemonset update
logic handles changes to image pullspecs and other important fields.
Together, the new end-to-end test and the existing unit tests should
provide sufficient test coverage for reconciliation of daemonsets.

* test/e2e/operator_test.go (TestCoreDNSDaemonSetReconciliation): New
test.  Verify that the operator reconciles the dns-default daemonset.

test/e2e/operator_test.go

@@ -176,6 +176,66 @@ func TestDefaultDNSSteadyConditions(t *testing.T) {
 	}
 }
 
+// TestCoreDNSDaemonSetReconciliation verifies that the operator reconciles the
+// dns-default daemonset.  The test modifies the daemonset and verifies that the
+// operator reverts the change.
+func TestCoreDNSDaemonSetReconciliation(t *testing.T) {
+	cl, err := getClient()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defaultDNS := &operatorv1.DNS{}
+	err = wait.PollImmediate(1*time.Second, 5*time.Minute, func() (bool, error) {
+		if err := cl.Get(context.TODO(), types.NamespacedName{Name: operatorcontroller.DefaultDNSController}, defaultDNS); err != nil {
+			t.Logf("failed to get dns %q: %v", operatorcontroller.DefaultDNSController, err)
+			return false, nil
+		}
+		return true, nil
+	})
+	if err != nil {
+		t.Fatalf("failed to get dns %q: %v", operatorcontroller.DefaultDNSController, err)
+	}
+
+	newNodeSelector := "foo"
+	namespacedName := operatorcontroller.DNSDaemonSetName(defaultDNS)
+	err = wait.PollImmediate(1*time.Second, 5*time.Minute, func() (bool, error) {
+		dnsDaemonSet := &appsv1.DaemonSet{}
+		if err := cl.Get(context.TODO(), namespacedName, dnsDaemonSet); err != nil {
+			t.Logf("failed to get daemonset %s: %v", namespacedName, err)
+			return false, nil
+		}
+		dnsDaemonSet.Spec.Template.Spec.NodeSelector[newNodeSelector] = ""
+		if err := cl.Update(context.TODO(), dnsDaemonSet); err != nil {
+			t.Logf("failed to update daemonset %s: %v", namespacedName, err)
+			return false, nil
+		}
+		return true, nil
+	})
+	if err != nil {
+		t.Errorf("failed to update daemonset %s: %v", namespacedName, err)
+	}
+
+	err = wait.PollImmediate(1*time.Second, 5*time.Minute, func() (bool, error) {
+		dnsDaemonSet := &appsv1.DaemonSet{}
+		if err := cl.Get(context.TODO(), namespacedName, dnsDaemonSet); err != nil {
+			t.Logf("failed to get daemonset %s: %v", namespacedName, err)
+			return false, nil
+		}
+		for k := range dnsDaemonSet.Spec.Template.Spec.NodeSelector {
+			if k == newNodeSelector {
+				t.Logf("found %q node selector on daemonset %s: %v", newNodeSelector, namespacedName, err)
+				return false, nil
+			}
+		}
+		t.Logf("observed absence of %q node selector on daemonset %s: %v", newNodeSelector, namespacedName, err)
+		return true, nil
+	})
+	if err != nil {
+		t.Errorf("failed to observe reversion of update to daemonset %s: %v", namespacedName, err)
+	}
+}
+
 func TestDNSForwarding(t *testing.T) {
 	cl, err := getClient()
 	if err != nil {