add tests

Author: qingyang-hu

bson/bsoncodec.go

@@ -69,6 +69,9 @@ func (vde ValueDecoderError) Error() string {
 	if vde.Received.IsValid() {
 		received = vde.Received.Type().String()
 	}
+	if !vde.Received.CanSet() {
+		received = "unsettable " + received
+	}
 	return fmt.Sprintf("%s can only decode valid and settable %s, but got %s", vde.Name, strings.Join(typeKinds, ", "), received)
 }
 

bson/decoder_test.go

@@ -172,6 +172,29 @@ func TestDecodingInterfaces(t *testing.T) {
 					assert.Equal(t, testStruct{[3]interface{}{&str, &i, nil}}, receiver)
 				}
 
+				return data, &receiver, check
+			},
+		},
+		{
+			name: "struct with interface slice containing concrete values",
+			stub: func() ([]byte, interface{}, func(*testing.T)) {
+				type testStruct struct {
+					Values []interface{}
+				}
+
+				data := docToBytes(struct {
+					Values []interface{}
+				}{
+					Values: []interface{}{1, 2, 3},
+				})
+
+				receiver := testStruct{[]interface{}{7, 8}}
+
+				check := func(t *testing.T) {
+					t.Helper()
+					assert.Equal(t, testStruct{[]interface{}{1, 2, int32(3)}}, receiver)
+				}
+
 				return data, &receiver, check
 			},
 		},

bson/unmarshal_test.go

@@ -422,6 +422,28 @@ func TestUnmarshalInterface(t *testing.T) {
 					assert.Equal(t, testStruct{[3]interface{}{&str, &i, nil}}, receiver)
 				}
 
+				return data, &receiver, check
+			},
+		},
+		{
+			name: "struct with interface slice containing concrete values",
+			stub: func() ([]byte, interface{}, func(*testing.T)) {
+				type testStruct struct {
+					Values []interface{}
+				}
+				data := docToBytes(struct {
+					Values []interface{}
+				}{
+					Values: []interface{}{1, 2, 3},
+				})
+
+				receiver := testStruct{[]interface{}{7, 8}}
+
+				check := func(t *testing.T) {
+					t.Helper()
+					assert.Equal(t, testStruct{[]interface{}{1, 2, int32(3)}}, receiver)
+				}
+
 				return data, &receiver, check
 			},
 		},