Demonstrate panic when a resource references a claim without references

Despite past negz's optimistic comment to the contrary, we can't assume the
class reference is set by the time we get to the dynamic provisioning stage.
We are queued for managed resources that reference a claim, so we could reach
the dynamic provisioning stage without a class reference being set if a managed
resource referenced a claim that had no class reference or resource reference.

Signed-off-by: Nic Cope <negz@rk0n.org>

pkg/resource/claim_binding_reconciler_test.go

@@ -311,6 +311,38 @@ func TestClaimReconciler(t *testing.T) {
 			},
 			want: want{result: reconcile.Result{Requeue: false}},
 		},
+		"ClassReferenceNotSet": {
+			args: args{
+				m: &MockManager{
+					c: &test.MockClient{
+						MockGet: test.NewMockGetFn(nil, func(o runtime.Object) error {
+							switch o := o.(type) {
+							case *MockClaim:
+								*o = MockClaim{}
+								return nil
+							case *MockManaged:
+								return nil
+							default:
+								return errUnexpected
+							}
+						}),
+						MockStatusUpdate: test.NewMockStatusUpdateFn(nil, func(got runtime.Object) error {
+							want := &MockClaim{}
+							want.SetConditions(Binding(), v1alpha1.ReconcileSuccess())
+							if diff := cmp.Diff(want, got, test.EquateConditions()); diff != "" {
+								t.Errorf("-want, +got:\n%s", diff)
+							}
+							return nil
+						}),
+					},
+					s: MockSchemeWith(&MockClaim{}, &MockClass{}, &MockManaged{}),
+				},
+				of:   ClaimKind(MockGVK(&MockClaim{})),
+				use:  ClassKind(MockGVK(&MockClass{})),
+				with: ManagedKind(MockGVK(&MockManaged{})),
+			},
+			want: want{result: reconcile.Result{Requeue: false}},
+		},
 		"GetResourceClassError": {
 			args: args{
 				m: &MockManager{