diff --git a/encoding/gocode/gen_test.go b/encoding/gocode/gen_test.go
new file mode 100644
index 0000000..6f01c2b
--- /dev/null
+++ b/encoding/gocode/gen_test.go
@@ -0,0 +1,89 @@
+// Copyright 2019 CUE 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.
+
+// +build !gen
+
+package gocode
+
+import (
+	"strings"
+	"testing"
+
+	"cuelang.org/go/encoding/gocode/testdata/pkg1"
+	"cuelang.org/go/encoding/gocode/testdata/pkg2"
+)
+
+func TestPackages(t *testing.T) {
+	testCases := []struct {
+		name string
+		got  error
+		want string
+	}{{
+		name: "failing int",
+		got: func() error {
+			v := pkg2.PickMe(4)
+			return v.Validate()
+		}(),
+		want: "invalid value 4 (out of bound >5):\n    pkg2/instance.cue:x:x",
+	}, {
+		name: "failing field with validator",
+		got: func() error {
+			v := &pkg1.OtherStruct{A: "car"}
+			return v.Validate()
+		}(),
+		want: "A: invalid value \"car\" (does not satisfy strings.ContainsAny(\"X\")):\n    pkg1/instance.cue:x:x",
+	}, {
+		name: "failing field of type int",
+		got: func() error {
+			v := &pkg1.MyStruct{A: 11, B: "dog"}
+			return v.Validate()
+		}(),
+		want: "A: invalid value 11 (out of bound <=10):\n    pkg1/instance.cue:x:x",
+	}, {
+		name: "failing nested struct ",
+		got: func() error {
+			v := &pkg1.MyStruct{A: 5, B: "dog", O: &pkg1.OtherStruct{A: "car"}}
+			return v.Validate()
+		}(),
+		want: "O.A: invalid value \"car\" (does not satisfy strings.ContainsAny(\"X\")):\n    pkg1/instance.cue:x:x",
+	}, {
+		name: "fail nested struct of different package",
+		got: func() error {
+			v := &pkg1.MyStruct{A: 5, B: "dog", O: &pkg1.OtherStruct{A: "X", P: 4}}
+			return v.Validate()
+		}(),
+		want: "O.P: invalid value 4 (out of bound >5):\n    pkg2/instance.cue:x:x",
+	}, {
+		name: "all good",
+		got: func() error {
+			v := &pkg1.MyStruct{
+				A: 5,
+				B: "dog",
+				I: &pkg2.ImportMe{A: 1000, B: "a"},
+			}
+			return v.Validate()
+		}(),
+		want: "nil",
+	}}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := strings.TrimSpace(errStr(tc.got))
+			want := tc.want
+			if got != want {
+				t.Errorf("got:\n%q\nwant:\n%q", got, want)
+			}
+
+		})
+	}
+}