Add packet padding container for packet length shaping

common/packetPaddingContainer/container_test.go

@@ -0,0 +1,113 @@
+package packetPaddingContainer_test
+
+import (
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+
+	"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/packetPaddingContainer"
+)
+
+func TestPacketPaddingContainer(t *testing.T) {
+	Convey("Given a PacketPaddingContainer", t, func() {
+		container := packetPaddingContainer.New()
+
+		Convey("When packing data with padding", func() {
+			data := []byte("testdata")
+			padding := 4
+			packedData := container.Pack(data, padding)
+
+			Convey("The packed data should have the correct length", func() {
+				expectedLength := len(data) + padding + 2
+				So(len(packedData), ShouldEqual, expectedLength)
+			})
+
+			Convey("When unpacking the packed data", func() {
+				unpackedData, unpackedPadding := container.Unpack(packedData)
+
+				Convey("The unpacked data should match the original data", func() {
+					So(string(unpackedData), ShouldEqual, string(data))
+				})
+
+				Convey("The unpacked padding should match the original padding", func() {
+					So(unpackedPadding, ShouldEqual, padding)
+				})
+			})
+		})
+
+		Convey("When packing empty data with padding", func() {
+			data := []byte("")
+			padding := 4
+			packedData := container.Pack(data, padding)
+
+			Convey("The packed data should have the correct length", func() {
+				expectedLength := len(data) + padding + 2
+				So(len(packedData), ShouldEqual, expectedLength)
+			})
+
+			Convey("When unpacking the packed data", func() {
+				unpackedData, unpackedPadding := container.Unpack(packedData)
+
+				Convey("The unpacked data should match the original data", func() {
+					So(string(unpackedData), ShouldEqual, string(data))
+				})
+
+				Convey("The unpacked padding should match the original padding", func() {
+					So(unpackedPadding, ShouldEqual, padding)
+				})
+			})
+		})
+
+		Convey("When packing data with zero padding", func() {
+			data := []byte("testdata")
+			padding := 0
+			packedData := container.Pack(data, padding)
+
+			Convey("The packed data should have the correct length", func() {
+				expectedLength := len(data) + padding + 2
+				So(len(packedData), ShouldEqual, expectedLength)
+			})
+
+			Convey("When unpacking the packed data", func() {
+				unpackedData, unpackedPadding := container.Unpack(packedData)
+
+				Convey("The unpacked data should match the original data", func() {
+					So(string(unpackedData), ShouldEqual, string(data))
+				})
+
+				Convey("The unpacked padding should match the original padding", func() {
+					So(unpackedPadding, ShouldEqual, padding)
+				})
+			})
+		})
+
+		Convey("When padding data", func() {
+			Convey("With a positive padding length", func() {
+				padLength := 3
+				padData := container.Pad(padLength)
+
+				Convey("The padded data should have the correct length", func() {
+					So(len(padData), ShouldEqual, padLength)
+				})
+			})
+
+			Convey("With a zero padding length", func() {
+				padLength := 0
+				padData := container.Pad(padLength)
+
+				Convey("The padded data should be empty", func() {
+					So(len(padData), ShouldEqual, 0)
+				})
+			})
+
+			Convey("With a negative padding length", func() {
+				padLength := -1
+				padData := container.Pad(padLength)
+
+				Convey("The padded data should be nil", func() {
+					So(padData, ShouldBeNil)
+				})
+			})
+		})
+	})
+}