[vtadmin] Add a vtctld Dialer unit test

Signed-off-by: Sara Bee <[email protected]>

go/vt/vtadmin/vtctldclient/proxy_test.go

@@ -0,0 +1,69 @@
+/*
+Copyright 2021 The Vitess 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 vtctldclient
+
+import (
+	"context"
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+
+	vtadminpb "vitess.io/vitess/go/vt/proto/vtadmin"
+	vtctlservicepb "vitess.io/vitess/go/vt/proto/vtctlservice"
+	"vitess.io/vitess/go/vt/vtadmin/cluster/discovery/fakediscovery"
+)
+
+type fakeVtctld struct {
+	vtctlservicepb.VtctlServer
+}
+
+func TestDial(t *testing.T) {
+	listener, err := net.Listen("tcp", ":0")
+	require.NoError(t, err)
+
+	defer listener.Close()
+
+	vtctld := &fakeVtctld{}
+	server := grpc.NewServer()
+	vtctlservicepb.RegisterVtctlServer(server, vtctld)
+
+	go server.Serve(listener)
+	defer server.Stop()
+
+	disco := fakediscovery.New()
+	disco.AddTaggedVtctlds(nil, &vtadminpb.Vtctld{
+		Hostname: listener.Addr().String(),
+	})
+
+	proxy := New(&Config{
+		Cluster: &vtadminpb.Cluster{
+			Id:   "test",
+			Name: "testcluster",
+		},
+		Discovery: disco,
+	})
+
+	// We don't have a vtctld host until we call Dial
+	require.Empty(t, proxy.host)
+
+	err = proxy.Dial(context.Background())
+	assert.NoError(t, err)
+	assert.Equal(t, listener.Addr().String(), proxy.host)
+}