Create a method to check dryRun is supported

We don't want to run dryRun requests against servers that don't support
dry-run, since they might ignore the flag and just persist the unwanted
changes.

This creates a new method that checks in the OpenAPI if the dryRun
parameter can be used.

pkg/kubectl/cmd/util/openapi/dryrun_test.go

@@ -0,0 +1,80 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+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.
+*/
+
+package openapi_test
+
+import (
+	"testing"
+
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/kubernetes/pkg/kubectl/cmd/util/openapi"
+)
+
+func TestSupportsDryRun(t *testing.T) {
+	doc, err := fakeSchema.OpenAPISchema()
+	if err != nil {
+		t.Fatalf("Failed to get OpenAPI Schema: %v", err)
+	}
+
+	tests := []struct {
+		gvk      schema.GroupVersionKind
+		success  bool
+		supports bool
+	}{
+		{
+			gvk: schema.GroupVersionKind{
+				Group:   "",
+				Version: "v1",
+				Kind:    "Pod",
+			},
+			success:  true,
+			supports: true,
+		},
+		{
+			gvk: schema.GroupVersionKind{
+				Group:   "",
+				Version: "v1",
+				Kind:    "UnknownKind",
+			},
+			success:  false,
+			supports: false,
+		},
+		{
+			gvk: schema.GroupVersionKind{
+				Group:   "",
+				Version: "v1",
+				Kind:    "NodeProxyOptions",
+			},
+			success:  true,
+			supports: false,
+		},
+	}
+
+	for _, test := range tests {
+		supports, err := openapi.SupportsDryRun(doc, test.gvk)
+		if supports != test.supports || ((err == nil) != test.success) {
+			errStr := "nil"
+			if test.success == false {
+				errStr = "err"
+			}
+			t.Errorf("SupportsDryRun(doc, %v) = (%v, %v), expected (%v, %v)",
+				test.gvk,
+				supports, err,
+				test.supports, errStr,
+			)
+		}
+	}
+}