diff --git a/checks/oop_advanced/oop_advanced10.py b/checks/oop_advanced/oop_advanced10.py
index 6d86d7a..d704466 100644
--- a/checks/oop_advanced/oop_advanced10.py
+++ b/checks/oop_advanced/oop_advanced10.py
@@ -1,3 +1,3 @@
-assert issubclass(Square, Shape)
-assert Square(4).area() == 16
-print("oop_advanced10 ok")
+assert issubclass(Square, Shape), "Square should inherit from Shape"
+assert Square(4).area() == 16, "Square(4).area() should be 16 (4 * 4)"
+print("oop_advanced10 ok")
diff --git a/checks/oop_advanced/oop_advanced11.py b/checks/oop_advanced/oop_advanced11.py
index 58c7645..4d1e6c5 100644
--- a/checks/oop_advanced/oop_advanced11.py
+++ b/checks/oop_advanced/oop_advanced11.py
@@ -1,3 +1,3 @@
-product = Product("book", 12)
-assert product.to_dict() == {"name": "book", "price": 12}
-print("oop_advanced11 ok")
+product = Product("book", 12)
+assert product.to_dict() == {"name": "book", "price": 12}, "Product('book', 12).to_dict() should return {'name': 'book', 'price': 12}"
+print("oop_advanced11 ok")
diff --git a/checks/oop_advanced/oop_advanced12.py b/checks/oop_advanced/oop_advanced12.py
index 37c1079..8ac6b1f 100644
--- a/checks/oop_advanced/oop_advanced12.py
+++ b/checks/oop_advanced/oop_advanced12.py
@@ -1,4 +1,4 @@
-result = Vector(1, 2) + Vector(3, 4)
-assert isinstance(result, Vector)
-assert (result.x, result.y) == (4, 6)
-print("oop_advanced12 ok")
+result = Vector(1, 2) + Vector(3, 4)
+assert isinstance(result, Vector), "Adding two Vector instances should return a Vector"
+assert (result.x, result.y) == (4, 6), "Vector(1,2) + Vector(3,4) should be (4, 6)"
+print("oop_advanced12 ok")
diff --git a/checks/oop_advanced/oop_advanced7.py b/checks/oop_advanced/oop_advanced7.py
index 6b54ae7..04c2215 100644
--- a/checks/oop_advanced/oop_advanced7.py
+++ b/checks/oop_advanced/oop_advanced7.py
@@ -1,3 +1,3 @@
-assert Book("A", "123") == Book("B", "123")
-assert Book("A", "123") != Book("C", "999")
-print("oop_advanced7 ok")
+assert Book("A", "123") == Book("B", "123"), "Two books with the same ISBN should be equal"
+assert Book("A", "123") != Book("C", "999"), "Two books with different ISBNs should not be equal"
+print("oop_advanced7 ok")
diff --git a/checks/oop_advanced/oop_advanced8.py b/checks/oop_advanced/oop_advanced8.py
index 11193f8..d1a81a1 100644
--- a/checks/oop_advanced/oop_advanced8.py
+++ b/checks/oop_advanced/oop_advanced8.py
@@ -1,3 +1,3 @@
-coord = Coordinate.from_text("3,4")
-assert (coord.x, coord.y) == (3, 4)
-print("oop_advanced8 ok")
+coord = Coordinate.from_text("3,4")
+assert (coord.x, coord.y) == (3, 4), "Coordinate.from_text('3,4') should produce x=3 and y=4"
+print("oop_advanced8 ok")
diff --git a/checks/oop_advanced/oop_advanced9.py b/checks/oop_advanced/oop_advanced9.py
index d187057..321856a 100644
--- a/checks/oop_advanced/oop_advanced9.py
+++ b/checks/oop_advanced/oop_advanced9.py
@@ -1,4 +1,4 @@
-assert Grade.is_valid(0) is True
-assert Grade.is_valid(100) is True
-assert Grade.is_valid(101) is False
-print("oop_advanced9 ok")
+assert Grade.is_valid(0) is True, "Grade 0 should be a valid score"
+assert Grade.is_valid(100) is True, "Grade 100 should be a valid score"
+assert Grade.is_valid(101) is False, "Grade 101 should be rejected as out of range"
+print("oop_advanced9 ok")