Add unit tests for stripPackagePrefix.

ygen/protogen.go

@@ -334,7 +334,9 @@ func writeProto3Msg(msg *yangDirectory, msgs map[string]*yangDirectory, state *g
 // code representing it. It uses the set of messages that have been extracted and the
 // current generator state to map to other messages and ensure uniqueness of names.
 // The configuration parameters for the current code generation required are supplied
-// as a protoMsgConfig struct.
+// as a protoMsgConfig struct. The parentPkg argument specifies the name of the parent
+// package for the protobuf message(s) that are being generated, such that relative
+// paths can be used in the messages.
 // TODO(robjs): Split the logic of this function into multiple subfunctions.
 func genProto3Msg(msg *yangDirectory, msgs map[string]*yangDirectory, state *genState, cfg protoMsgConfig, parentPkg string) ([]protoMsg, []error) {
 	var errs []error

ygen/protogen_test.go

@@ -1506,3 +1506,34 @@ func TestUnionFieldToOneOf(t *testing.T) {
 		}
 	}
 }
+
+func TestStripPackagePrefix(t *testing.T) {
+	tests := []struct {
+		name     string
+		inPrefix string
+		inPath   string
+		want     string
+	}{{
+		name:     "invalid prefix at element one",
+		inPrefix: "one.two",
+		inPath:   "two.four",
+		want:     "two.four",
+	}, {
+		name:     "single element prefix",
+		inPrefix: "one",
+		inPath:   "one.three",
+		want:     "three",
+	}, {
+		name:     "longer prefix",
+		inPrefix: "one.two.three",
+		inPath:   "one.two.three.five",
+		want:     "five",
+	}}
+
+	for _, tt := range tests {
+		if got := stripPackagePrefix(tt.inPrefix, tt.inPath); got != tt.want {
+			t.Errorf("%s: stripPackagePrefix(%s, %s): did not get expected output, got: %s, want: %s", tt.name, tt.inPrefix, tt.inPath, got, tt.want)
+		}
+	}
+
+}