Added check server-side validation error message check

Author: seans3

pkg/client/client_test.go

@@ -242,6 +242,7 @@ var _ = Describe("Client", func() {
 			By("creating the pod, since required field Containers is empty")
 			err = cl.Create(context.TODO(), pod)
 			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(ContainSubstring("is invalid"))
 
 			close(done)
 		}, serverSideTimeoutSeconds)