Example code on how to mock gRPC services

examples/helloworld/mock/generate_mock.sh

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+mockgen google.golang.org/grpc/examples/helloworld/helloworld GreeterClient > mock_helloworld/hw_mock.go
+gofmt -w mock_helloworld/hw_mock.go

examples/helloworld/mock/hw_test.go

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+package mock
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	proto "github.com/golang/protobuf/proto"
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/examples/helloworld/helloworld"
+	hwmock "google.golang.org/grpc/examples/helloworld/mock/mock_helloworld"
+)
+
+// rpcMsg implements the gomock.Matcher interface
+type rpcMsg struct {
+	msg proto.Message
+}
+
+func (r *rpcMsg) Matches(msg interface{}) bool {
+	m, ok := msg.(proto.Message)
+	if !ok {
+		return false
+	}
+	return proto.Equal(m, r.msg)
+}
+
+func (r *rpcMsg) String() string {
+	return fmt.Sprintf("is %s", r.msg)
+}
+
+func TestSayHello(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	mockGreeterClient := hwmock.NewMockGreeterClient(ctrl)
+	req := &helloworld.HelloRequest{Name: "unit_test"}
+	mockGreeterClient.EXPECT().SayHello(
+		gomock.Any(),
+		&rpcMsg{msg: req},
+	).Return(&helloworld.HelloReply{Message: "Mocked Interface"}, nil)
+	testSayHello(t, mockGreeterClient)
+}
+
+func testSayHello(t *testing.T, client helloworld.GreeterClient) {
+	r, err := client.SayHello(context.Background(), &helloworld.HelloRequest{Name: "unit_test"})
+	if err != nil || r.Message != "Mocked Interface" {
+		t.Errorf("mocking failed")
+	}
+	t.Log("Reply : ", r.Message)
+}

examples/helloworld/mock/mock_helloworld/hw_mock.go

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+// Automatically generated by MockGen. DO NOT EDIT!
+// Source: google.golang.org/grpc/examples/helloworld/helloworld (interfaces: GreeterClient)
+
+package mock_helloworld
+
+import (
+	gomock "github.com/golang/mock/gomock"
+	context "golang.org/x/net/context"
+	grpc "google.golang.org/grpc"
+	helloworld "google.golang.org/grpc/examples/helloworld/helloworld"
+)
+
+// Mock of GreeterClient interface
+type MockGreeterClient struct {
+	ctrl     *gomock.Controller
+	recorder *_MockGreeterClientRecorder
+}
+
+// Recorder for MockGreeterClient (not exported)
+type _MockGreeterClientRecorder struct {
+	mock *MockGreeterClient
+}
+
+func NewMockGreeterClient(ctrl *gomock.Controller) *MockGreeterClient {
+	mock := &MockGreeterClient{ctrl: ctrl}
+	mock.recorder = &_MockGreeterClientRecorder{mock}
+	return mock
+}
+
+func (_m *MockGreeterClient) EXPECT() *_MockGreeterClientRecorder {
+	return _m.recorder
+}
+
+func (_m *MockGreeterClient) SayHello(_param0 context.Context, _param1 *helloworld.HelloRequest, _param2 ...grpc.CallOption) (*helloworld.HelloReply, error) {
+	_s := []interface{}{_param0, _param1}
+	for _, _x := range _param2 {
+		_s = append(_s, _x)
+	}
+	ret := _m.ctrl.Call(_m, "SayHello", _s...)
+	ret0, _ := ret[0].(*helloworld.HelloReply)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+func (_mr *_MockGreeterClientRecorder) SayHello(arg0, arg1 interface{}, arg2 ...interface{}) *gomock.Call {
+	_s := append([]interface{}{arg0, arg1}, arg2...)
+	return _mr.mock.ctrl.RecordCall(_mr.mock, "SayHello", _s...)
+}