Add required tests for go/mysql/hex (#14976)

Signed-off-by: Noble Mittal <[email protected]>

go/mysql/hex/hex_test.go

@@ -0,0 +1,102 @@
+/*
+Copyright 2024 The Vitess 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.
+*/
+
+package hex
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEncodeBytes(t *testing.T) {
+	testCases := []struct {
+		input []byte
+		want  []byte
+	}{
+		{[]byte{0xAB, 0xCD, 0xEF}, []byte("ABCDEF")},
+		{[]byte{0x01, 0x23, 0x45}, []byte("012345")},
+	}
+
+	for _, tCase := range testCases {
+		got := EncodeBytes(tCase.input)
+		assert.Equal(t, tCase.want, got)
+	}
+}
+
+func TestEncodeUint(t *testing.T) {
+	testCases := []struct {
+		input uint64
+		want  []byte
+	}{
+		{0, []byte("0")},
+		{123, []byte("7B")},
+		{255, []byte("FF")},
+		{4096, []byte("1000")},
+	}
+
+	for _, tCase := range testCases {
+		got := EncodeUint(tCase.input)
+		assert.Equal(t, tCase.want, got)
+	}
+}
+
+func TestDecodeUint(t *testing.T) {
+	testCases := []struct {
+		input uint64
+		want  []byte
+	}{
+		{0, []byte{0}},
+		{123, []byte{0x01, 0x23}},
+		{255, []byte{0x02, 0x55}},
+		{4096, []byte{0x40, 0x96}},
+	}
+
+	for _, tCase := range testCases {
+		got := DecodeUint(tCase.input)
+		assert.Equal(t, tCase.want, got)
+	}
+}
+
+func TestDecodedLen(t *testing.T) {
+	testCases := []struct {
+		input []byte
+		want  int
+	}{
+		{[]byte{0}, 1},
+		{[]byte{0x01, 0x23}, 1},
+		{[]byte("ABCDE"), 3},
+		{[]byte("0123456789ABCDEF"), 8},
+	}
+
+	for _, tCase := range testCases {
+		got := DecodedLen(tCase.input)
+		assert.Equal(t, tCase.want, got)
+	}
+}
+
+func TestDecodeBytes(t *testing.T) {
+	err := DecodeBytes([]byte("testDst"), []byte("1"))
+	assert.NoError(t, err)
+
+	err = DecodeBytes([]byte("testDst"), []byte("12"))
+	assert.NoError(t, err)
+
+	// DecodeBytes should return an error for "é" as
+	// hex.decode returns an error for non-ASCII characters
+	err = DecodeBytes([]byte("testDst"), []byte("é"))
+	assert.Error(t, err)
+}