func TestResourceProvider_diff_error(t *testing.T) {
	p := new(terraform.MockResourceProvider)
	client, server := testClientServer(t)
	name, err := Register(server, p)
	if err != nil {
		t.Fatalf("err: %s", err)
	}
	provider := &ResourceProvider{Client: client, Name: name}

	p.DiffReturnError = errors.New("foo")

	// Diff
	info := &terraform.InstanceInfo{}
	state := &terraform.InstanceState{}
	config := &terraform.ResourceConfig{
		Raw: map[string]interface{}{"foo": "bar"},
	}
	diff, err := provider.Diff(info, state, config)
	if !p.DiffCalled {
		t.Fatal("diff should be called")
	}
	if !reflect.DeepEqual(p.DiffDesired, config) {
		t.Fatalf("bad: %#v", p.DiffDesired)
	}
	if err == nil {
		t.Fatal("should have error")
	}
	if diff != nil {
		t.Fatal("should not have diff")
	}
}