diff --git a/src/additions/test_pass.py b/src/additions/test_pass.py
index 57a6de9b..1c21623f 100644
--- a/src/additions/test_pass.py
+++ b/src/additions/test_pass.py
@@ -15,7 +15,9 @@ def test_pass_in_function():
 
     The pass statement below is silently ignored but it makes current test_pass() function valid.
     """
-    pass
+    print('test')
+    # pass
+
 
 
 def test_pass_in_loop():
@@ -43,4 +45,4 @@ class MyEmptyClass:
 
     "Pass" is commonly used for creating minimal classes like current one.
     """
-    pass
+    # pass
diff --git a/src/classes/test_class_and_instance_variables.py b/src/classes/test_class_and_instance_variables.py
index c4004d79..f17d2a69 100644
--- a/src/classes/test_class_and_instance_variables.py
+++ b/src/classes/test_class_and_instance_variables.py
@@ -84,3 +84,5 @@ def add_trick(self, trick):
 
     assert fido.tricks == ['roll over']
     assert buddy.tricks == ['play dead']
+
+    # Good to learn class variable
diff --git a/src/classes/test_class_objects.py b/src/classes/test_class_objects.py
index 2d5a4cdb..73428259 100644
--- a/src/classes/test_class_objects.py
+++ b/src/classes/test_class_objects.py
@@ -21,7 +21,7 @@ def test_class_objects():
     # attribute references:
 
     class ComplexNumber:
-        """Example of the complex numbers class"""
+        """Try to write some doc"""
 
         real = 0
         imaginary = 0
@@ -37,7 +37,7 @@ def get_imaginary(self):
     assert ComplexNumber.real == 0
 
     # __doc__ is also a valid attribute, returning the docstring belonging to the class
-    assert ComplexNumber.__doc__ == 'Example of the complex numbers class'
+    assert ComplexNumber.__doc__ == 'Try to write some doc'
 
     # Class attributes can also be assigned to, so you can change the value of
     # ComplexNumber.counter by assignment.
diff --git a/src/classes/test_inheritance.py b/src/classes/test_inheritance.py
index 5884da2c..707fead2 100644
--- a/src/classes/test_inheritance.py
+++ b/src/classes/test_inheritance.py
@@ -38,6 +38,8 @@ class Employee(Person):
     in the global scope.)
     """
     def __init__(self, name, staff_id):
+        Person.__init__(self, name)
+        # This is a new feature to me
         Person.__init__(self, name)
         # You may also use super() here in order to avoid explicit using of parent class name:
         # >>> super().__init__(name)
@@ -79,3 +81,5 @@ def test_inheritance():
 
     assert issubclass(Employee, Person)
     assert not issubclass(Person, Employee)
+
+    assert not issubclass(Employee, Exception)
diff --git a/src/classes/test_instance_objects.py b/src/classes/test_instance_objects.py
index e58dc343..e65fbc4c 100644
--- a/src/classes/test_instance_objects.py
+++ b/src/classes/test_instance_objects.py
@@ -28,3 +28,10 @@ class DummyClass:
     dummy_instance.temporary_attribute = 1
     assert dummy_instance.temporary_attribute == 1
     del dummy_instance.temporary_attribute
+
+    # I didn't know the data attributes need not to be declared
+    dummy_instance.idontknow = True
+    assert dummy_instance.idontknow == True
+    del dummy_instance.idontknow
+    assert dummy_instance.__doc__ == "Dummy class"
+    assert DummyClass.__doc__ == "Dummy class"
diff --git a/src/control_flow/test_for.py b/src/control_flow/test_for.py
index 7411277b..3fe6b096 100644
--- a/src/control_flow/test_for.py
+++ b/src/control_flow/test_for.py
@@ -34,6 +34,8 @@ def test_for_statement():
         if len(word) > 6:
             words.insert(0, word)
 
+    # This is an important tip
+
     # Otherwise with for w in words:, the example would attempt to create an infinite list,
     # inserting defenestrate over and over again.
 
diff --git a/src/data_types/test_dictionaries.py b/src/data_types/test_dictionaries.py
index da3b9cc8..54cfaef3 100644
--- a/src/data_types/test_dictionaries.py
+++ b/src/data_types/test_dictionaries.py
@@ -31,6 +31,7 @@ def test_dictionary():
     }
 
     assert isinstance(fruits_dictionary, dict)
+    assert not isinstance(fruits_dictionary, list)
 
     # You may access set elements by keys.
     assert fruits_dictionary['apple'] == 'green'
@@ -59,6 +60,7 @@ def test_dictionary():
 
     # The dict() constructor builds dictionaries directly from sequences of key-value pairs.
     dictionary_via_constructor = dict([('sape', 4139), ('guido', 4127), ('jack', 4098)])
+    assert {'a': 1, 'b': 2, 'c': 3} == dict([('a', 1), ('b', 2), ('c', 3)])
 
     assert dictionary_via_constructor['sape'] == 4139
     assert dictionary_via_constructor['guido'] == 4127
@@ -74,6 +76,8 @@ def test_dictionary():
     # When the keys are simple strings, it is sometimes easier to specify pairs using
     # keyword arguments.
     dictionary_for_string_keys = dict(sape=4139, guido=4127, jack=4098)
+
+    assert dict(xy=1, yz=2, xz=3) == {'xy':  1, 'yz': 2, "xz": 3}
     assert dictionary_for_string_keys['sape'] == 4139
     assert dictionary_for_string_keys['guido'] == 4127
     assert dictionary_for_string_keys['jack'] == 4098
diff --git a/src/data_types/test_lists.py b/src/data_types/test_lists.py
index 33ffdbe9..8450005a 100644
--- a/src/data_types/test_lists.py
+++ b/src/data_types/test_lists.py
@@ -274,6 +274,8 @@ def test_list_comprehensions():
     vector = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
     flatten_vector = [num for elem in vector for num in elem]
     assert flatten_vector == [1, 2, 3, 4, 5, 6, 7, 8, 9]
+    test_flatten = [[2, 3, 4], [1, 2, 3], [4, 3, 2]]
+    assert [i for elm in test_flatten for i in elm] == [2, 3, 4, 1, 2, 3, 4, 3, 2]
 
 
 def test_nested_list_comprehensions():
diff --git a/src/data_types/test_strings.py b/src/data_types/test_strings.py
index ae86432f..9959813f 100644
--- a/src/data_types/test_strings.py
+++ b/src/data_types/test_strings.py
@@ -137,6 +137,12 @@ def test_string_operators():
         'to have them joined together.'
     )
     assert text == 'Put several strings within parentheses to have them joined together.'
+    my_trial = (
+        "This is a new feature "
+        "Good to know this!"
+        "\n"
+    )
+    assert my_trial == "This is a new feature Good to know this!\n"
 
     # If you want to concatenate variables or a variable and a literal, use +:
     prefix = 'Py'
diff --git a/src/data_types/test_tuples.py b/src/data_types/test_tuples.py
index b122824e..27194931 100644
--- a/src/data_types/test_tuples.py
+++ b/src/data_types/test_tuples.py
@@ -63,6 +63,11 @@ def test_tuples():
     assert len(singleton_tuple) == 1
     assert singleton_tuple == ('hello',)
 
+    my_singleton = 'abc',
+    assert my_singleton == ('abc', )
+    my_singleton2 = 'this ', 'is', 'new',
+    assert  my_singleton2 == ('this ', 'is', 'new', )
+
     # The following example is called tuple packing:
     packed_tuple = 12345, 54321, 'hello!'
 
diff --git a/src/exceptions/test_handle_exceptions.py b/src/exceptions/test_handle_exceptions.py
index 342561a3..04336cdc 100644
--- a/src/exceptions/test_handle_exceptions.py
+++ b/src/exceptions/test_handle_exceptions.py
@@ -104,3 +104,5 @@ def test_handle_exceptions():
 
     assert not exception_has_been_handled
     assert no_exceptions_has_been_fired
+
+    # Good to learn this feature
\ No newline at end of file
diff --git a/src/exceptions/test_raise_exceptions.py b/src/exceptions/test_raise_exceptions.py
index 3d5ede1c..9ae81943 100644
--- a/src/exceptions/test_raise_exceptions.py
+++ b/src/exceptions/test_raise_exceptions.py
@@ -19,6 +19,7 @@ def test_raise_exception():
         # exception class is passed, it will be implicitly instantiated by calling its constructor
         # with no arguments
         raise NameError('HiThere')  # shorthand for 'raise ValueError()'
+        raise NameError("someerror")
     except NameError:
         exception_is_caught = True
 
@@ -41,6 +42,20 @@ def __init__(self, message):
 
     custom_exception_is_caught = False
 
+    class My1stError(Exception):
+        """Try by myself"""
+        def __init__(self, msg):
+            super().__init__(msg)
+            self.message = msg
+
+    my1stexception = False
+    try:
+        raise My1stError("My 1st error msg")
+    except My1stError:
+        my1stexception = True
+
+    assert my1stexception == True
+
     try:
         raise MyCustomError('My custom message')
     except MyCustomError:
diff --git a/src/functions/test_function_annotations.py b/src/functions/test_function_annotations.py
index 4c6495e6..f3c2ad07 100644
--- a/src/functions/test_function_annotations.py
+++ b/src/functions/test_function_annotations.py
@@ -15,7 +15,6 @@
 
 def breakfast(ham: str, eggs: str = 'eggs') -> str:
     """Breakfast creator.
-
     This function has a positional argument, a keyword argument, and the return value annotated.
     """
     return ham + ' and ' + eggs
@@ -25,3 +24,6 @@ def test_function_annotations():
     """Function Annotations."""
 
     assert breakfast.__annotations__ == {'eggs': str, 'ham': str, 'return': str}
+    assert breakfast.__doc__ == """Breakfast creator.
+    This function has a positional argument, a keyword argument, and the return value annotated.
+    """
\ No newline at end of file
diff --git a/src/functions/test_function_arbitrary_arguments.py b/src/functions/test_function_arbitrary_arguments.py
index b3f36627..435abccf 100644
--- a/src/functions/test_function_arbitrary_arguments.py
+++ b/src/functions/test_function_arbitrary_arguments.py
@@ -31,3 +31,6 @@ def concat(*args, sep='/'):
 
     assert concat('earth', 'mars', 'venus') == 'earth/mars/venus'
     assert concat('earth', 'mars', 'venus', sep='.') == 'earth.mars.venus'
+
+def test_my_arbitrary_arguments():
+    """Test arbitrary argument list"""
diff --git a/src/functions/test_function_default_arguments.py b/src/functions/test_function_default_arguments.py
index aa2a09ad..a1bd9a2d 100644
--- a/src/functions/test_function_default_arguments.py
+++ b/src/functions/test_function_default_arguments.py
@@ -24,3 +24,8 @@ def test_default_function_arguments():
     # We may also want to override the second argument by using the following function calls.
     assert power_of(3, 2) == 9
     assert power_of(3, 3) == 27
+    assert my_func(4) == 2 ** 3 / 4
+
+def my_func(division, number = 2, power = 3):
+    return number ** power / division
+
diff --git a/src/functions/test_function_definition.py b/src/functions/test_function_definition.py
index 82a0b50b..44491934 100644
--- a/src/functions/test_function_definition.py
+++ b/src/functions/test_function_definition.py
@@ -94,6 +94,11 @@ def call_func(func):
 
     assert call_func(greet_one_more) == 'Hello, John'
 
+    def my_test(name):
+        return 'My name is: {}'.format(name)
+
+    assert call_func(my_test) == 'My name is: John'
+
     # Functions can return other functions. In other words, functions generating other functions.
 
     def compose_greet_func():
@@ -118,6 +123,19 @@ def get_message():
 
         return get_message
 
+    def compose_modify_outer_varialbe(name):
+        age = 10
+
+        def get_message():
+            # age = 3
+            return "{} age is : {}".format(name, age)
+
+        assert age == 10
+        return get_message
+
+    modify_outer_closure = compose_modify_outer_varialbe('John')
+    assert modify_outer_closure() == 'John age is : 10'
+
     greet_with_closure = compose_greet_func_with_closure('John')
 
     assert greet_with_closure() == 'Hello there, John!'
diff --git a/src/functions/test_function_keyword_arguments.py b/src/functions/test_function_keyword_arguments.py
index 65d066c1..e273858f 100644
--- a/src/functions/test_function_keyword_arguments.py
+++ b/src/functions/test_function_keyword_arguments.py
@@ -117,3 +117,5 @@ def test_function(first_param, *arguments, **keywords):
         fourth_param_name='fourth named param',
         fifth_param_name='fifth named param',
     )
+
+    # useful
\ No newline at end of file
diff --git a/src/functions/test_function_scopes.py b/src/functions/test_function_scopes.py
index 5d3525e5..258f1303 100644
--- a/src/functions/test_function_scopes.py
+++ b/src/functions/test_function_scopes.py
@@ -105,3 +105,5 @@ def test_global_variable_access():
     # it was changed by "someone" and you need to know about the CONTEXT of who had changed that.
     # So once again access global and non local scope only if you know what you're doing otherwise
     # it might be considered as bad practice.
+
+    # nonlocal, global
\ No newline at end of file
diff --git a/src/getting_started/test_variables.py b/src/getting_started/test_variables.py
index d41e777a..a83546c3 100644
--- a/src/getting_started/test_variables.py
+++ b/src/getting_started/test_variables.py
@@ -36,3 +36,10 @@ def test_variables():
     variable_with_changed_type = 'Sally'  # x is now of type str
 
     assert variable_with_changed_type == 'Sally'
+
+def test_my_variables():
+    """Test my own variables"""
+    ab_cdd_e = 1
+    my_name = "Evan"
+    assert ab_cdd_e == 1
+    assert my_name == "Evan"
diff --git a/src/modules/test_modules.py b/src/modules/test_modules.py
index 7f919d61..5cab8cb9 100644
--- a/src/modules/test_modules.py
+++ b/src/modules/test_modules.py
@@ -95,3 +95,5 @@ def test_modules():
         'fibonacci_at_position',
         'fibonacci_smaller_than',
     ]
+
+
diff --git a/src/operators/test_arithmetic.py b/src/operators/test_arithmetic.py
index fa66ad66..a7c76f16 100644
--- a/src/operators/test_arithmetic.py
+++ b/src/operators/test_arithmetic.py
@@ -42,3 +42,14 @@ def test_arithmetic_operators():
     assert 7 // 3 == 2
     assert 9 // 3 == 3
     assert isinstance(5 // 3, int)
+
+def test_my_arithetic_operators():
+    """my operators"""
+    # addition
+    assert 5 + 5 == 10
+    # subtraction
+    assert 90 - 90.0 == 0.0
+    assert isinstance(5 / 3, float)
+    assert isinstance(4 / 2, float)
+
+    assert 8 + 8 == 16