diff --git a/aiogram/api/types/inline_keyboard_markup.py b/aiogram/api/types/inline_keyboard_markup.py
index 43fcec9e..d5dcb5ef 100644
--- a/aiogram/api/types/inline_keyboard_markup.py
+++ b/aiogram/api/types/inline_keyboard_markup.py
@@ -18,16 +18,18 @@ class InlineKeyboardMarkup(MutableTelegramObject):
     Source: https://core.telegram.org/bots/api#inlinekeyboardmarkup
     """
 
-    row_width: int = 3
-    inline_keyboard: List[List[InlineKeyboardButton]] = []
+    inline_keyboard: List[List[InlineKeyboardButton]] = list()
     """Array of button rows, each represented by an Array of InlineKeyboardButton objects"""
 
+    row_width: int = 3
+    """Wight of row. New buttons will fit this limit."""
+
     def add(self, *args: InlineKeyboardButton) -> InlineKeyboardMarkup:
         """
         Add buttons
+
         :param args:
         :return: self
-        :rtype: :obj:`types.InlineKeyboardMarkup`
         """
         row = []
         for index, button in enumerate(args, start=1):
@@ -42,9 +44,9 @@ class InlineKeyboardMarkup(MutableTelegramObject):
     def row(self, *args: InlineKeyboardButton) -> InlineKeyboardMarkup:
         """
         Add row
+
         :param args:
         :return: self
-        :rtype: :obj:`types.InlineKeyboardMarkup`
         """
         btn_array = []
         for button in args:
@@ -55,9 +57,9 @@ class InlineKeyboardMarkup(MutableTelegramObject):
     def insert(self, button: InlineKeyboardButton) -> InlineKeyboardMarkup:
         """
         Insert button to last row
+
         :param button:
         :return: self
-        :rtype: :obj:`types.InlineKeyboardMarkup`
         """
         if self.inline_keyboard and len(self.inline_keyboard[-1]) < self.row_width:
             self.inline_keyboard[-1].append(button)
diff --git a/tests/test_api/test_types/test_inline_keyboard_markup.py b/tests/test_api/test_types/test_inline_keyboard_markup.py
new file mode 100644
index 00000000..fd357ee8
--- /dev/null
+++ b/tests/test_api/test_types/test_inline_keyboard_markup.py
@@ -0,0 +1,54 @@
+import pytest
+
+from aiogram.api.types import InlineKeyboardButton, InlineKeyboardMarkup
+
+test_row_width = [1, 2, 3, 10]
+test_inline_keyboard = [
+    [],
+    [
+        [
+            InlineKeyboardButton(text="foo", url="https://google.com"),
+            InlineKeyboardButton(text="foo", url="https://google.com"),
+        ]
+    ],
+]
+
+
+class TestInlineKeyboardMarkup:
+    @pytest.mark.parametrize("row_width", test_row_width)
+    def test_keyboard_markup_add(self, row_width):
+        kwargs = dict(row_width=row_width, inline_keyboard=[])
+
+        button = InlineKeyboardButton(text="foo", url="https://google.com")
+
+        keyboard_markup = InlineKeyboardMarkup(**kwargs)
+
+        api_method = keyboard_markup.add(button)
+
+        assert button in api_method.inline_keyboard[0]
+
+    @pytest.mark.parametrize("row_width", test_row_width)
+    def test_keyboard_markup_row(self, row_width):
+        kwargs = dict(row_width=row_width, inline_keyboard=[])
+        buttons = [
+            InlineKeyboardButton(text="foo", url="https://google.com"),
+            InlineKeyboardButton(text="bar", callback_data="test"),
+        ]
+
+        keyboard_markup = InlineKeyboardMarkup(**kwargs)
+
+        api_method = keyboard_markup.row(*buttons)
+
+        assert buttons == api_method.inline_keyboard[0]
+
+    @pytest.mark.parametrize("row_width", test_row_width)
+    @pytest.mark.parametrize("inline_keyboard", test_inline_keyboard)
+    def test_keyboard_markup_insert(self, row_width, inline_keyboard):
+        kwargs = dict(row_width=row_width, inline_keyboard=inline_keyboard)
+        button = InlineKeyboardButton(text="foo", url="https://google.com")
+
+        keyboard_markup = InlineKeyboardMarkup(**kwargs)
+
+        api_method = keyboard_markup.insert(button)
+
+        assert button in api_method.inline_keyboard[0]