diff --git a/telegram/formatter/formatter_test.go b/telegram/formatter/formatter_test.go
index 187d486..aaaca89 100644
--- a/telegram/formatter/formatter_test.go
+++ b/telegram/formatter/formatter_test.go
@@ -1,13 +1,28 @@
 package formatter
 
 import (
+	"errors"
+	"strings"
 	"testing"
 
 	"github.com/zelenin/go-tdlib/client"
 )
 
+type MentionRetrieverMock struct {}
+
+func (m *MentionRetrieverMock) GetMUCNicknameByUsername(username string) (string, error) {
+	if strings.HasPrefix(username, "@") {
+		return username[1:], nil
+	}
+	return "", errors.New("Я@ТЫ@Я@ТЫ@Я@ТЫ@Я@ТЫ@Я@ТЫ@")
+}
+
+func (m *MentionRetrieverMock) GetMUCNickname(id int64) (string) {
+	return "42"
+}
+
 func TestNoFormatting(t *testing.T) {
-	markup := Format("abc\ndef", []*client.TextEntity{}, MarkupModeMarkdown)
+	markup := Format("abc\ndef", []*client.TextEntity{}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "abc\ndef" {
 		t.Errorf("No formatting expected, but: %v", markup)
 	}
@@ -20,7 +35,7 @@ func TestFormattingSimple(t *testing.T) {
 			Length: 4,
 			Type:   &client.TextEntityTypeBold{},
 		},
-	}, MarkupModeMarkdown)
+	}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "👙**🐧🐖**" {
 		t.Errorf("Wrong simple formatting: %v", markup)
 	}
@@ -40,7 +55,7 @@ func TestFormattingAdjacent(t *testing.T) {
 				Url: "https://narayana.im/",
 			},
 		},
-	}, MarkupModeMarkdown)
+	}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "a👙_🐧_[🐖](https://narayana.im/)" {
 		t.Errorf("Wrong adjacent formatting: %v", markup)
 	}
@@ -63,7 +78,7 @@ func TestFormattingAdjacentAndNested(t *testing.T) {
 			Length: 2,
 			Type:   &client.TextEntityTypeItalic{},
 		},
-	}, MarkupModeMarkdown)
+	}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "```\n**👙**🐧\n```_🐖_" {
 		t.Errorf("Wrong adjacent&nested formatting: %v", markup)
 	}
@@ -208,7 +223,7 @@ func TestSortEmpty(t *testing.T) {
 }
 
 func TestNoFormattingXEP0393(t *testing.T) {
-	markup := Format("abc\ndef", []*client.TextEntity{}, MarkupModeXEP0393)
+	markup := Format("abc\ndef", []*client.TextEntity{}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "abc\ndef" {
 		t.Errorf("No formatting expected, but: %v", markup)
 	}
@@ -221,7 +236,7 @@ func TestFormattingXEP0393Simple(t *testing.T) {
 			Length: 4,
 			Type:   &client.TextEntityTypeBold{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "👙*🐧🐖*" {
 		t.Errorf("Wrong simple formatting: %v", markup)
 	}
@@ -241,7 +256,7 @@ func TestFormattingXEP0393Adjacent(t *testing.T) {
 				Url: "https://narayana.im/",
 			},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "a👙_🐧_🐖 <https://narayana.im/>" {
 		t.Errorf("Wrong adjacent formatting: %v", markup)
 	}
@@ -264,7 +279,7 @@ func TestFormattingXEP0393AdjacentAndNested(t *testing.T) {
 			Length: 2,
 			Type:   &client.TextEntityTypeItalic{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "```\n*👙*🐧\n```_🐖_" {
 		t.Errorf("Wrong adjacent&nested formatting: %v", markup)
 	}
@@ -287,7 +302,7 @@ func TestFormattingXEP0393AdjacentItalicBoldItalic(t *testing.T) {
 			Length: 69,
 			Type:   &client.TextEntityTypeItalic{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "_раса двуногих крысолюдей, *которую так редко замечают, что многие отрицают само их существование*_" {
 		t.Errorf("Wrong adjacent italic/bold-italic formatting: %v", markup)
 	}
@@ -315,7 +330,7 @@ func TestFormattingXEP0393MultipleAdjacent(t *testing.T) {
 			Length: 1,
 			Type:   &client.TextEntityTypeItalic{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "a*bcd*_e_" {
 		t.Errorf("Wrong multiple adjacent formatting: %v", markup)
 	}
@@ -343,7 +358,7 @@ func TestFormattingXEP0393Intersecting(t *testing.T) {
 			Length: 1,
 			Type:   &client.TextEntityTypeBold{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "a*b*_*cd*e_" {
 		t.Errorf("Wrong intersecting formatting: %v", markup)
 	}
@@ -361,7 +376,7 @@ func TestFormattingXEP0393InlineCode(t *testing.T) {
 			Length: 25,
 			Type:   &client.TextEntityTypePre{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "Is `Gajim` a thing?\n\n```\necho 'Hello'\necho 'world'\n```\n\nhruck(" {
 		t.Errorf("Wrong intersecting formatting: %v", markup)
 	}
@@ -374,7 +389,7 @@ func TestFormattingMarkdownStrikethrough(t *testing.T) {
 			Length: 3,
 			Type:   &client.TextEntityTypeStrikethrough{},
 		},
-	}, MarkupModeMarkdown)
+	}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "Everyone ~~dis~~likes cake." {
 		t.Errorf("Wrong strikethrough formatting: %v", markup)
 	}
@@ -387,7 +402,7 @@ func TestFormattingXEP0393Strikethrough(t *testing.T) {
 			Length: 3,
 			Type:   &client.TextEntityTypeStrikethrough{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "Everyone ~dis~likes cake." {
 		t.Errorf("Wrong strikethrough formatting: %v", markup)
 	}
@@ -480,7 +495,7 @@ func TestNoNewlineBlockquoteXEP0393(t *testing.T) {
 			Length: 6,
 			Type:   &client.TextEntityTypeBlockQuote{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "yes \n> it can\n i think" {
 		t.Errorf("Wrong blockquote formatting: %v", markup)
 	}
@@ -493,7 +508,7 @@ func TestNoNewlineBlockquoteMarkdown(t *testing.T) {
 			Length: 6,
 			Type:   &client.TextEntityTypeBlockQuote{},
 		},
-	}, MarkupModeMarkdown)
+	}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "yes \n> it can\n\n i think" {
 		t.Errorf("Wrong blockquote formatting: %v", markup)
 	}
@@ -506,7 +521,7 @@ func TestMultilineBlockquoteXEP0393(t *testing.T) {
 			Length: 17,
 			Type:   &client.TextEntityTypeBlockQuote{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "> hruck\n> puck\n> \n> shuck\ntext" {
 		t.Errorf("Wrong blockquote formatting: %v", markup)
 	}
@@ -519,7 +534,7 @@ func TestMultilineBlockquoteMarkdown(t *testing.T) {
 			Length: 17,
 			Type:   &client.TextEntityTypeBlockQuote{},
 		},
-	}, MarkupModeMarkdown)
+	}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "> hruck\npuck\n\n> shuck\n\ntext" {
 		t.Errorf("Wrong blockquote formatting: %v", markup)
 	}
@@ -547,7 +562,7 @@ func TestMixedBlockquoteXEP0393(t *testing.T) {
 			Length: 2,
 			Type:   &client.TextEntityTypeStrikethrough{},
 		},
-	}, MarkupModeXEP0393)
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
 	if markup != "> *_hruck\n> p~uc~k_\n> shuck*\ntext" {
 		t.Errorf("Wrong blockquote formatting: %v", markup)
 	}
@@ -575,8 +590,83 @@ func TestMixedBlockquoteMarkdown(t *testing.T) {
 			Length: 2,
 			Type:   &client.TextEntityTypeStrikethrough{},
 		},
-	}, MarkupModeMarkdown)
+	}, MarkupModeMarkdown, &MentionRetrieverMock{})
 	if markup != "> **_hruck\np~~uc~~k_\nshuck**\n\ntext" {
 		t.Errorf("Wrong blockquote formatting: %v", markup)
 	}
 }
+
+func TestUsernameMention(t *testing.T) {
+	markup := Format("a @b c", []*client.TextEntity{
+		&client.TextEntity{
+			Offset: 2,
+			Length: 2,
+			Type:   &client.TextEntityTypeMention{},
+		},
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
+	if markup != "a b c" {
+		t.Errorf("Wrong mention formatting: %v", markup)
+	}
+}
+
+func TestUsernameMentionName(t *testing.T) {
+	markup := Format("a bb c", []*client.TextEntity{
+		&client.TextEntity{
+			Offset: 2,
+			Length: 2,
+			Type:   &client.TextEntityTypeMentionName{UserId: 100500},
+		},
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
+	if markup != "a 42 c" {
+		t.Errorf("Wrong mention name formatting: %v", markup)
+	}
+}
+
+func TestUsernameMentionNested(t *testing.T) {
+	markup := Format("a @b c", []*client.TextEntity{
+		&client.TextEntity{
+			Offset: 2,
+			Length: 2,
+			Type:   &client.TextEntityTypeMention{},
+		},
+		&client.TextEntity{
+			Offset: 2,
+			Length: 1,
+			Type:   &client.TextEntityTypeBold{},
+		},
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
+	if markup != "a b c" {
+		t.Errorf("Wrong formatting of mention with nested entity: %v", markup)
+	}
+}
+
+func TestUsernameMentionNestedEven(t *testing.T) {
+	markup := Format("a @b c", []*client.TextEntity{
+		&client.TextEntity{
+			Offset: 2,
+			Length: 2,
+			Type:   &client.TextEntityTypeMention{},
+		},
+		&client.TextEntity{
+			Offset: 2,
+			Length: 2,
+			Type:   &client.TextEntityTypeBold{},
+		},
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
+	if markup != "a *b* c" {
+		t.Errorf("Wrong formatting of mention with even nested entity: %v", markup)
+	}
+}
+
+func TestUsernameMentionError(t *testing.T) {
+	markup := Format("a bb c", []*client.TextEntity{
+		&client.TextEntity{
+			Offset: 2,
+			Length: 2,
+			Type:   &client.TextEntityTypeMention{},
+		},
+	}, MarkupModeXEP0393, &MentionRetrieverMock{})
+	if markup != "a bb c" {
+		t.Errorf("Wrong formatting of erroneous mention: %v", markup)
+	}
+}