tests: implement b.EditReplyMarkup() function test

bot.go

@@ -726,24 +726,29 @@ func (b *Bot) Edit(msg Editable, what interface{}, options ...interface{}) (*Mes
 }
 
 // EditReplyMarkup used to edit reply markup of already sent message.
+// Pass nil or empty ReplyMarkup to delete it from the message.
 //
-// On success, returns edited message object
+// On success, returns edited message object.
+// This function will panic upon nil Editable.
 func (b *Bot) EditReplyMarkup(message Editable, markup *ReplyMarkup) (*Message, error) {
 	messageID, chatID := message.MessageSig()
-
 	params := map[string]string{}
 
-	// if inline message
-	if chatID == 0 {
+	if chatID == 0 { // if inline message
 		params["inline_message_id"] = messageID
 	} else {
 		params["chat_id"] = strconv.FormatInt(chatID, 10)
 		params["message_id"] = messageID
 	}
 
+	if markup == nil {
+		// will delete reply markup
+		markup = &ReplyMarkup{}
+	}
+
 	processButtons(markup.InlineKeyboard)
-	jsonMarkup, _ := json.Marshal(markup)
-	params["reply_markup"] = string(jsonMarkup)
+	data, _ := json.Marshal(markup)
+	params["reply_markup"] = string(data)
 
 	data, err := b.Raw("editMessageReplyMarkup", params)
 	if err != nil {

bot_test.go

@@ -4,6 +4,7 @@ import (
 	"net/http"
 	"os"
 	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -332,4 +333,30 @@ func TestBot(t *testing.T) {
 		assert.NoError(t, err)
 		assert.NotNil(t, msg.Location)
 	})
+
+	t.Run("EditReplyMarkup()", func(t *testing.T) {
+		markup := &ReplyMarkup{
+			InlineKeyboard: [][]InlineButton{{{
+				Data: "btn",
+				Text: "Hi Telebot!",
+			}}},
+		}
+		badMarkup := &ReplyMarkup{
+			InlineKeyboard: [][]InlineButton{{{
+				Data: strings.Repeat("*", 65),
+				Text: "Bad Button",
+			}}},
+		}
+
+		msg, err := b.EditReplyMarkup(msg, markup)
+		assert.NoError(t, err)
+		assert.Equal(t, msg.ReplyMarkup.InlineKeyboard, markup.InlineKeyboard)
+
+		msg, err = b.EditReplyMarkup(msg, nil)
+		assert.NoError(t, err)
+		assert.Nil(t, msg.ReplyMarkup.InlineKeyboard)
+
+		_, err = b.EditReplyMarkup(msg, badMarkup)
+		assert.Equal(t, ErrButtonDataInvalid, err)
+	})
 }