diff --git a/.gitignore b/.gitignore
index 3d76c77..8de69c4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,4 +11,5 @@ venv*/
 
 # VS Code IDE
 /.vscode/
-*.code-workspace
\ No newline at end of file
+<<<<<<< HEAD
+*.code-workspace
diff --git a/README.md b/README.md
index d0a76f3..2e32b07 100644
--- a/README.md
+++ b/README.md
@@ -2,3 +2,18 @@
 # File server project
 
 Author is Vasyl Pidhirskyi.
+
+## Сделанные требования
+
+Get port and working directory via arguments
+Work independently without WSGI
+Suit with RESTful API requirements
+Provide sharing access to files and access policy
+Protect files by cryptography tools
+Use asynchronous programming concept
+Work with database
+Use multithreading for downloading files
+
+## Желаемые требования
+
+TODO: заполните требования
diff --git a/demo/docstrings/demo.py b/demo/docstrings/demo.py
new file mode 100644
index 0000000..361eb71
--- /dev/null
+++ b/demo/docstrings/demo.py
@@ -0,0 +1,31 @@
+"""This is demo module.
+
+It contains a lof useful functions.
+Here you can find a class `MyClass`.
+"""
+
+
+class MyClass:
+    @staticmethod
+    def sum(a: int, b: int) -> int:
+        """Sum the values of two numbers.
+
+        Args:
+            a (int): number 1
+            b (int): number 2
+
+        Returns:
+            This is a description of what is returned.
+
+        Raises:
+            KeyError: Raises an exception.
+        """
+        return a + b
+
+
+print(dir(MyClass.sum))
+print("__annotations__:", MyClass.sum.__annotations__)
+print("__doc__:", MyClass.sum.__doc__)
+print("call:", MyClass.sum(1, 2))
+print("call:", MyClass.sum("bug", "bug"))
+print("call:", MyClass.sum(1, "bug"))
diff --git a/demo/docstrings/docstring.md b/demo/docstrings/docstring.md
new file mode 100644
index 0000000..4b448de
--- /dev/null
+++ b/demo/docstrings/docstring.md
@@ -0,0 +1,16 @@
+
+# Documentation
+
+https://www.python.org/dev/peps/pep-0257/
+https://docs.python-guide.org/writing/documentation/
+
+
+# Different styles
+
+https://stackoverflow.com/questions/3898572/what-is-the-standard-python-docstring-format
+
+
+#
+
+- VS Code extension njpwerner.autodocstring
+- PyCharm settings
diff --git a/demo/exceptions/demo1.py b/demo/exceptions/demo1.py
new file mode 100644
index 0000000..b76e338
--- /dev/null
+++ b/demo/exceptions/demo1.py
@@ -0,0 +1,11 @@
+def summa(n1, n2):
+    if type(n1) != 'int':
+        # TODO: show stack trace
+        raise TypeError('incorrect type: {}'.format(type(n1)))
+    return n1 - n2
+
+
+try:
+    summa('a', 'b')
+except (TypeError, RuntimeError) as e:
+    print("error occurred {}".format(e.message))
diff --git a/demo/exceptions/exc_add_message.py b/demo/exceptions/exc_add_message.py
new file mode 100644
index 0000000..4bbcd4b
--- /dev/null
+++ b/demo/exceptions/exc_add_message.py
@@ -0,0 +1,11 @@
+try:
+    with open(path, "r") as f:
+        return dict(name=f.name,
+                    content=f.read(),
+                    create_date=time.strftime('%d.%M.%Y %H:%M:%S', time.gmtime(os.path.getctime(path))),
+                    edit_date=time.strftime('%d.%M.%Y %H:%M:%S', time.gmtime(os.path.getmtime(path))),
+                    size=int(os.path.getsize(path)))
+except RuntimeError as err:
+    e.args += ('Custom message',)
+    ...
+
diff --git a/demo/exceptions/exception_main.py b/demo/exceptions/exception_main.py
new file mode 100644
index 0000000..ec9ca2c
--- /dev/null
+++ b/demo/exceptions/exception_main.py
@@ -0,0 +1,6 @@
+if __name__ == '__main__':
+    try:
+        main()
+    except BaseException as err:
+        # logging
+        print("всё плохо {}".format(err))
diff --git a/demo/exceptions/try-except.py b/demo/exceptions/try-except.py
new file mode 100644
index 0000000..d0a9024
--- /dev/null
+++ b/demo/exceptions/try-except.py
@@ -0,0 +1,6 @@
+try:
+    d = int(input('>'))
+    x = 2 / d
+    print(x)
+except Exception as e:
+    print(e)
\ No newline at end of file
diff --git a/demo/modules/example1/__init__.py b/demo/modules/example1/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/demo/modules/example1/mod1.py b/demo/modules/example1/mod1.py
new file mode 100644
index 0000000..9393533
--- /dev/null
+++ b/demo/modules/example1/mod1.py
@@ -0,0 +1,11 @@
+# import mymodules.mod2
+
+name = 'Me'
+
+
+def whoami():
+    print(name)
+
+
+print("mod1: {}".format(__name__))
+started = True
diff --git a/demo/modules/example1/modules.md b/demo/modules/example1/modules.md
new file mode 100644
index 0000000..e69de29
diff --git a/demo/modules/example1/mymodules/__init__.py b/demo/modules/example1/mymodules/__init__.py
new file mode 100644
index 0000000..93c9be9
--- /dev/null
+++ b/demo/modules/example1/mymodules/__init__.py
@@ -0,0 +1,3 @@
+import mod2
+
+print('mymodules started')
diff --git a/demo/modules/example1/mymodules/mod2.py b/demo/modules/example1/mymodules/mod2.py
new file mode 100644
index 0000000..bd9413b
--- /dev/null
+++ b/demo/modules/example1/mymodules/mod2.py
@@ -0,0 +1,5 @@
+def hello():
+    print("Hello, world")
+
+
+print("mod2: {}".format(__name__))
diff --git a/demo/modules/example2/changer.py b/demo/modules/example2/changer.py
new file mode 100644
index 0000000..6565871
--- /dev/null
+++ b/demo/modules/example2/changer.py
@@ -0,0 +1,3 @@
+import config
+
+config.globalvar = '0'
diff --git a/demo/modules/example2/config.py b/demo/modules/example2/config.py
new file mode 100644
index 0000000..7790c68
--- /dev/null
+++ b/demo/modules/example2/config.py
@@ -0,0 +1,2 @@
+
+globalvar = 'default'
diff --git a/demo/modules/example2/main.py b/demo/modules/example2/main.py
new file mode 100644
index 0000000..a143a46
--- /dev/null
+++ b/demo/modules/example2/main.py
@@ -0,0 +1,28 @@
+import config
+import changer
+import config as baseConfig
+from config import globalvar as g  # separate variable --> it's a copy, so changes don't affect it
+
+print('--- step 0 ---')
+print(f'config.globalvar: {config.globalvar}')
+print(f'baseConfig.globalvar: {baseConfig.globalvar}')
+print(f'g: {g}')
+
+print('--- step 1 ---')
+config.globalvar = '1'
+print(f'config.globalvar: {config.globalvar}')
+print(f'baseConfig.globalvar: {baseConfig.globalvar}')
+print(f'g: {g}')
+
+print('--- step 2 ---')
+baseConfig.globalvar = '2'
+print(f'config.globalvar: {config.globalvar}')
+print(f'baseConfig.globalvar: {baseConfig.globalvar}')
+print(f'g: {g}')
+
+
+print('--- step 3 ---')
+g = '3'
+print(f'config.globalvar: {config.globalvar}')
+print(f'baseConfig.globalvar: {baseConfig.globalvar}')
+print(f'g: {g}')
diff --git a/demo/modules/example3/main.py b/demo/modules/example3/main.py
new file mode 100644
index 0000000..442772c
--- /dev/null
+++ b/demo/modules/example3/main.py
@@ -0,0 +1,5 @@
+import mypackage
+
+mypackage.init_function()
+mypackage.mymodule.myfunction()
+mypackage.f13()
diff --git a/demo/modules/example3/mypackage/__init__.py b/demo/modules/example3/mypackage/__init__.py
new file mode 100644
index 0000000..f6ee282
--- /dev/null
+++ b/demo/modules/example3/mypackage/__init__.py
@@ -0,0 +1,9 @@
+
+# other good examples:
+# https://github.com/pallets/flask/blob/main/src/flask/__init__.py
+
+from . import mymodule
+from .mymodule import myfunction as f13
+
+def init_function():
+    return True
diff --git a/demo/modules/example3/mypackage/mymodule.py b/demo/modules/example3/mypackage/mymodule.py
new file mode 100644
index 0000000..cca9f43
--- /dev/null
+++ b/demo/modules/example3/mypackage/mymodule.py
@@ -0,0 +1,3 @@
+
+def myfunction():
+    return 13
diff --git a/demo/ospath/ospath.md b/demo/ospath/ospath.md
new file mode 100644
index 0000000..4c33971
--- /dev/null
+++ b/demo/ospath/ospath.md
@@ -0,0 +1,65 @@
+
+# Работа с файловой системой
+
+Широко используются два модуля `os` и `os.path`.
+
+## Модуль `os`
+
+[Документация `os`](https://docs.python.org/3/library/os.html)
+
+Модуль используется для работы с файлами на диске:
+
+os.chdir(path) - установить текущий каталог
+os.getcwd() - получить текущий каталог
+os.listdir(path='.') - получить список файлов в каталоге
+
+os.makedirs(name, mode=0o777, exist_ok=False) - создать папку (с вложенными папками)
+os.mkdir(path, mode=0o777) - создать папку (родительские папки должны быть уже созданы)
+
+os.remove(path) - удалить файл
+os.rmdir(path) - удалить пустую папку
+os.removedirs(name) - удалить непустую папку
+
+Есть также функции по переименования, переносу файлов и другие.
+
+## Модуль `os.path`
+
+[Документация `os.path`](https://docs.python.org/3/library/os.path.html)
+
+Используется для работы с файловым путём:
+
+os.path.dirname(path) - получить имя родительской папки
+
+```python
+>>> os.path.dirname('c:\\1\\2\\3.txt')
+'c:\\1\\2'
+```
+
+os.path.join(path, *paths) - соединить несколько папок в один путь
+
+```python
+>>> os.path.join(os.getcwd(), 'data')
+'C:\\Work\\TC\\Trainings\\My\\python\\script-007\\demo\\argparsing\\data'
+
+>>> os.path.join(os.getcwd(), 'data', 'testfiles')
+'C:\\Work\\TC\\Trainings\\My\\python\\script-007\\demo\\argparsing\\data\\testfiles'
+```
+
+os.path.lexists(path) - проверить, что файл или папка существует
+
+```python
+>>> os.path.exists('c:\\1')
+False
+
+>>> os.path.exists('c:\\')
+True
+```
+
+os.path.is*(path) - проверить что объект является контретным типом
+
+os.path.islink(path)
+os.path.isdir(path)
+os.path.isfile(path)
+
+
+os.path.getsize(path) - получить размер файла
diff --git a/demo/tests/__init__.py b/demo/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/demo/tests/myfuncs.py b/demo/tests/myfuncs.py
new file mode 100644
index 0000000..47622f5
--- /dev/null
+++ b/demo/tests/myfuncs.py
@@ -0,0 +1,17 @@
+import os
+
+
+def myadd(a, b):
+    if a > 100:
+        return 100
+    return a + b
+
+
+def tricky_func():
+    a = 1
+    b = a + 1
+    return b
+
+
+def checkfile(filename):
+    return os.path.isfile(filename)
diff --git a/demo/tests/mypytests/.coveragerc b/demo/tests/mypytests/.coveragerc
new file mode 100644
index 0000000..8a888f3
--- /dev/null
+++ b/demo/tests/mypytests/.coveragerc
@@ -0,0 +1,4 @@
+[run]
+omit = tests/mypytests/*
+       tests/myunittests/*
+       tests/__init__.py
diff --git a/demo/tests/mypytests/__init__.py b/demo/tests/mypytests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/demo/tests/mypytests/conftest.py b/demo/tests/mypytests/conftest.py
new file mode 100644
index 0000000..0c37597
--- /dev/null
+++ b/demo/tests/mypytests/conftest.py
@@ -0,0 +1,16 @@
+import os
+
+import pytest
+
+
+@pytest.fixture(scope='function')
+def prepare_testfile(request):
+    print('prepare_testfile: before test')
+    with open('testfile.txt', 'w') as f:
+        f.write('first line')
+
+    yield  # Run tests
+
+    print('prepare_testfile: after test')
+    if os.path.exists('testfile.txt'):
+        os.remove('testfile.txt')
diff --git a/demo/tests/mypytests/pytest.md b/demo/tests/mypytests/pytest.md
new file mode 100644
index 0000000..b95fc95
--- /dev/null
+++ b/demo/tests/mypytests/pytest.md
@@ -0,0 +1,127 @@
+
+# Documentation
+
+https://docs.pytest.org/en/latest/getting-started.html
+
+[Naming conventions](https://docs.pytest.org/en/6.2.x/reference.html#confval-python_classes):
+
+- files matching `test_*.py` and `*_test.py` will be considered test modules
+- class names must start with `Test` and miss the `__init__` method
+- pytest will consider any function prefixed with `test` as a test
+
+# Run tests
+
+Usage:
+
+```console
+$ pytest [options] [file_or_dir] [file_or_dir] [...]
+```
+
+Success example:
+
+```console
+$ pytest tests/mypytests
+$ pytest tests/mypytests/test_0_myadd.py
+```
+
+# Capture output
+
+https://docs.pytest.org/en/6.2.x/capture.html
+
+Extra summary info can be shown using the '-r' option:
+
+```console
+$ pytest --help | rg -e -r -C 3
+  -r chars              show extra test summary info as specified by chars:
+                        (f)ailed, (E)rror, (s)kipped, (x)failed, (X)passed,
+                        (p)assed, (P)assed with output, (a)ll except passed
+                        (p/P), or (A)ll. Warnings are displayed at all times
+```
+
+shows the captured output of passed tests:
+
+```console
+$ pytest -rP
+```
+
+shows the captured output of failed tests (default behaviour):
+
+```console
+$ pytest -rx
+```
+
+`-s` allows seeing output as is.
+
+# Coverage
+
+There is a plugin [pytest-cov](https://pypi.org/project/pytest-cov/) to measure code coverage:
+
+```console
+$ pip install pytest-cov
+```
+
+Options are here:
+- https://pytest-cov.readthedocs.io/en/latest/config.html#reference
+- https://github.com/pytest-dev/pytest-cov/blob/master/src/pytest_cov/plugin.py
+
+Enable coverage:
+
+```console
+$ pytest --cov tests tests\mypytests
+============================= test session starts =============================
+platform win32 -- Python 2.7.18, pytest-4.6.11, py-1.10.0, pluggy-0.13.1
+rootdir: C:\Work\TC\Trainings\My\python\script-007\demo
+plugins: cov-2.12.1
+collected 12 items                                                             
+
+tests\mypytests\test_0_myadd.py .                                        [  8%]
+tests\mypytests\test_1_myadd_parametrize.py ...                          [ 33%]
+tests\mypytests\test_2_before_after.py ....                              [ 66%]
+tests\mypytests\test_3_conftest.py ..                                    [ 83%]
+tests\mypytests\test_4_class.py ..                                       [100%]
+
+---------- coverage: platform win32, python 2.7.18-final-0 -----------
+Name                                          Stmts   Miss  Cover
+-----------------------------------------------------------------
+tests\__init__.py                                 0      0   100%
+tests\myfuncs.py                                 11      4    64%
+tests\mypytests\__init__.py                       0      0   100%
+tests\mypytests\conftest.py                      10      0   100%
+tests\mypytests\test_0_myadd.py                   6      0   100%
+tests\mypytests\test_1_myadd_parametrize.py       4      0   100%
+tests\mypytests\test_2_before_after.py           22      0   100%
+tests\mypytests\test_3_conftest.py                6      0   100%
+tests\mypytests\test_4_class.py                  15      0   100%
+tests\myunittests\__init__.py                     0      0   100%
+tests\myunittests\test_checkfile.py              14     14     0%
+tests\myunittests\test_myadd.py                  11     11     0%
+-----------------------------------------------------------------
+TOTAL                                            99     29    71%
+
+
+========================== 12 passed in 0.32 seconds ==========================
+```
+
+Create HTML report:
+
+```console
+$ pytest --cov tests --cov-report=html tests\mypytests
+...
+---------- coverage: platform win32, python 2.7.18-final-0 -----------
+Coverage HTML written to dir htmlcov
+```
+
+Omit some modules, files:
+
+```console
+$ cat tests\mypytests\.coveragerc
+[run]
+omit = tests/mypytests/*
+       tests/myunittests/*
+       tests/__init__.py
+
+$ pytest --cov tests tests\mypytests --cov-config=tests\mypytests\.coveragerc
+```
+
+See other possibilities of `coverage` in [config file](https://coverage.readthedocs.io/en/latest/config.html#).
+
diff --git a/demo/tests/mypytests/requirements.txt b/demo/tests/mypytests/requirements.txt
new file mode 100644
index 0000000..0c69b77
--- /dev/null
+++ b/demo/tests/mypytests/requirements.txt
@@ -0,0 +1,3 @@
+pytest
+coverage
+pytest-cov
diff --git a/demo/tests/mypytests/test_0_myadd.py b/demo/tests/mypytests/test_0_myadd.py
new file mode 100644
index 0000000..80b78e9
--- /dev/null
+++ b/demo/tests/mypytests/test_0_myadd.py
@@ -0,0 +1,15 @@
+from tests.myfuncs import myadd
+
+
+def test_myadd():
+    myadd_dataset = [
+        0, 0, 0,
+        1, 2, 3,
+        11, -5, 6,
+        # 11, 5,  6,  # broken
+    ]
+
+    for i in range(0, len(myadd_dataset), 3):
+        a, b, c = myadd_dataset[i:i + 3]
+        # assert is not a function!
+        assert c == myadd(a, b)
diff --git a/demo/tests/mypytests/test_1_myadd_parametrize.py b/demo/tests/mypytests/test_1_myadd_parametrize.py
new file mode 100644
index 0000000..27e8cc9
--- /dev/null
+++ b/demo/tests/mypytests/test_1_myadd_parametrize.py
@@ -0,0 +1,14 @@
+import pytest
+
+from tests.myfuncs import myadd
+
+
+@pytest.mark.parametrize("num1, num2, sum", [
+    (0, 0, 0),     # test-case 1
+    (1, 2, 3),     # test-case 2
+    (11, -5, 6),   # test-case 3
+    (11, 1, 12),   # test-case 4
+    # (11, 5, 6),  # broken
+])
+def test_myadd(num1, num2, sum):
+    assert myadd(num1, num2) == sum
diff --git a/demo/tests/mypytests/test_1_myadd_parametrize2.py b/demo/tests/mypytests/test_1_myadd_parametrize2.py
new file mode 100644
index 0000000..659a9ea
--- /dev/null
+++ b/demo/tests/mypytests/test_1_myadd_parametrize2.py
@@ -0,0 +1,43 @@
+from http import HTTPStatus
+
+import pytest
+import requests
+
+from config import BASE_API_URL
+
+
+def test_login__correct_user__user_logged_in(test_user):
+    response = requests.post(
+        url=f"{BASE_API_URL}/login_web",
+        json={"username": test_user["username"], "password": test_user["password"]},
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    resp_data = response.json()
+    token_web = resp_data.pop("token_web", None)
+    assert token_web is not None, "No token_web in response"
+    assert resp_data == {"username": test_user["username"], "roles": []}
+
+
+@pytest.mark.parametrize(
+    argnames=("test_username", "test_password"),
+    argvalues=(
+        ("test", ""),
+        ("test", "wrong_pass"),
+        ("wrong_user", "some_pass"),
+    ),
+    ids=(
+        "empty password",
+        "wrong password",
+        "wrong user",
+    ),
+)
+def test_login__incorrect_user__user_failed_to_login(test_username, test_password):
+    response = requests.post(
+        url=f"{BASE_API_URL}/login_web",
+        json={"username": test_username, "password": test_password},
+    )
+
+    resp_data = response.json()
+    assert response.status_code == HTTPStatus.FORBIDDEN
+    assert resp_data == {"error": "Wrong username or password!"}
diff --git a/demo/tests/mypytests/test_2_before_after.py b/demo/tests/mypytests/test_2_before_after.py
new file mode 100644
index 0000000..50676a2
--- /dev/null
+++ b/demo/tests/mypytests/test_2_before_after.py
@@ -0,0 +1,42 @@
+import pytest
+
+
+@pytest.fixture(scope='class', autouse=True)  # Fixture, which executes before test suite implicitly
+def suite_implicit(request):
+    print('suite_implicit: before test')
+
+
+@pytest.fixture(scope='class')  # Fixture, which executes before test suite explicitly
+def suite_explicit(request):
+    print('suite_explicit: before test')
+
+
+@pytest.fixture(scope='function', autouse=True)  # Fixture, which executes before and after test case implicitly
+def case_implicit(request):
+    print('case_implicit: before test-case')
+    yield  # Run test case, transfer execution
+    print('case_implicit: after test-case')
+
+
+@pytest.fixture(scope='function')  # Fixture, which executes before and after test case explicitly
+def case_explicit(request):
+    print('case_explicit: before test-case')
+    yield  # Run test case, transfer execution
+    print('case_explicit: after test-case')
+
+
+# Test suite
+class TestSuite:
+
+    # Test cases
+    def testcase3(self, case_explicit):
+        print('I like cookies')
+
+    def testcase2(self, suite_explicit):
+        pass
+
+    def testcase1(self, suite_explicit, case_explicit):  # Add fixtures to test case
+        pass
+
+    def testcase4(self):
+        pass
diff --git a/demo/tests/mypytests/test_3_get_data.py b/demo/tests/mypytests/test_3_get_data.py
new file mode 100644
index 0000000..d25f6dd
--- /dev/null
+++ b/demo/tests/mypytests/test_3_get_data.py
@@ -0,0 +1,39 @@
+import pytest
+
+myvar = None
+
+
+@pytest.fixture(scope='function', autouse=True)
+def case_implicit_var(request):
+    print('case_implicit_var: before test-case')
+    global myvar
+    myvar = 'CASE_IMPLICIT_VAR'
+    yield myvar
+    print('case_implicit_var: after test-case')
+
+
+@pytest.fixture(scope='function', autouse=True)
+def case_implicit(request):
+    print('case_implicit: before test-case')
+    yield 'CASE_IMPLICIT'
+    print('case_implicit: after test-case')
+
+
+@pytest.fixture(scope='function')
+def case_explicit(request):
+    print('case_explicit: before test-case')
+    yield 'CASE_EXPLICIT'
+    print('case_explicit: after test-case')
+
+
+class TestSuite:
+
+    def testcase1(self):
+        print('testcase1: {}'.format(myvar))
+
+    def testcase2(self, case_explicit):
+        print('testcase2: {}'.format(case_explicit))
+
+    # if we need data from a fixture, then we can added it explicitly
+    def testcase3(self, case_implicit):
+        print('testcase3: {}'.format(case_implicit))
diff --git a/demo/tests/mypytests/test_4_get_data_class.py b/demo/tests/mypytests/test_4_get_data_class.py
new file mode 100644
index 0000000..0e0f41b
--- /dev/null
+++ b/demo/tests/mypytests/test_4_get_data_class.py
@@ -0,0 +1,25 @@
+import pytest
+
+
+@pytest.fixture(scope='function')
+def get_driver(request):
+    print('driver init')
+    driver = 'mydriver'  # init
+    request.cls.driver = driver
+    yield
+    driver = None  # deinit
+
+
+class TestUserDriver1:
+
+    @pytest.mark.usefixtures('get_driver')
+    def test_case1(self):
+        print('test_case1: {}'.format(self.driver))
+        assert self.driver == 'mydriver'
+
+
+class TestUserDriver2:
+
+    def test_case2(self, get_driver):
+        print('test_case2: {}'.format(self.driver))
+        assert self.driver == 'mydriver'
diff --git a/demo/tests/mypytests/test_5_conftest.py b/demo/tests/mypytests/test_5_conftest.py
new file mode 100644
index 0000000..d310f62
--- /dev/null
+++ b/demo/tests/mypytests/test_5_conftest.py
@@ -0,0 +1,10 @@
+from tests.myfuncs import checkfile
+
+
+class TestCheckFile:
+
+    def test_existent(self, prepare_testfile):
+        assert checkfile('testfile.txt')
+
+    def test_nonexistent(self, prepare_testfile):
+        assert not checkfile('testfile123.txt')
diff --git a/demo/tests/mypytests/test_6_exceptions.py b/demo/tests/mypytests/test_6_exceptions.py
new file mode 100644
index 0000000..d39ad44
--- /dev/null
+++ b/demo/tests/mypytests/test_6_exceptions.py
@@ -0,0 +1,20 @@
+import os
+
+import pytest
+
+# More information about exception handling
+# https://docs.pytest.org/en/6.2.x/assert.html#assertions-about-expected-exceptions
+
+
+class TestExceptions:
+
+    def test_exception(self):
+        with pytest.raises(AttributeError):
+            x = {'a': 1, 'b': 2}
+            print(x.a)
+
+    def test_few_exceptions(self):
+        # on Windows and Linux
+        with pytest.raises((WindowsError, OSError)):
+            os.chdir('NotExistingDirectory')
+
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..a044654
--- /dev/null
+++ b/main.py
@@ -0,0 +1,25 @@
+#!/usr/bin/env python3
+from server import FileService
+import argparse
+import logging
+import os
+
+PARENT_DIR = 'data'
+
+def main():
+    logging.debug('Start server')
+    os.chdir(os.path.join(os.getcwd(), PARENT_DIR))
+    aparser = argparse.ArgumentParser()
+    aparser.add_argument("-d", required=False, type=str, default=os.getcwd(), help="Change work directory")
+
+    args = aparser.parse_args()
+
+    if args.d:
+        FileService.change_dir(path=args.d)
+
+    logging.debug('Stop server')
+
+
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.DEBUG)
+    main()
diff --git a/requirements.txt b/requirements.txt
index e69de29..4342311 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -0,0 +1,3 @@
+pytest
+pytest-cov
+coverage
\ No newline at end of file
diff --git a/server/FileService.py b/server/FileService.py
new file mode 100644
index 0000000..35f4037
--- /dev/null
+++ b/server/FileService.py
@@ -0,0 +1,179 @@
+import os
+import time
+import logging
+
+
+def get_path(filename: str) -> str:
+    path = os.path.join(os.getcwd(), filename)
+    if not is_valid_path(path):
+        raise ValueError(f"Invalid filename {path}")
+
+    return path
+
+
+def is_valid_path(path: str) -> bool:
+    forbidden = """# %&{}\<>*?/$!'":@+`|="""
+    return bool(next((i for i in path if i not in forbidden), None))
+
+
+def is_allowed_path(path) -> bool:
+    return os.getcwd() in os.path.abspath(path)
+
+
+def change_dir(path: str, autocreate: bool = True) -> None:
+    """Change current directory of app.
+
+    Args:
+        path (str): Path to working directory with files.
+        autocreate (bool): Create folder if it doesn't exist.
+
+    Raises:
+        RuntimeError: if directory does not exist and autocreate is False.
+        ValueError: if path is invalid.
+    """
+
+    if not is_valid_path(path):
+        raise ValueError(f"Invalid path {path}")
+
+    if not is_allowed_path(path):
+        raise ValueError(f"Restricted path {path}")
+
+    if not os.path.exists(path):
+        if autocreate:
+            os.makedirs(path)
+        else:
+            raise RuntimeError(f"Directory does not exist and autocreate is False.")
+
+    os.chdir(path)
+    logging.debug(f"Set working directory to {os.getcwd()}")
+
+
+def get_files() -> list:
+    """Get info about all files in working directory.
+
+    Returns:
+        List of dicts, which contains info about each file. Keys:
+        - name (str): filename
+        - create_date (datetime): date of file creation.
+        - edit_date (datetime): date of last file modification.
+        - size (int): size of file in bytes.
+    """
+
+    folder = os.getcwd()
+    files = list()
+    for path in os.listdir(folder):
+        if os.path.isfile(path):
+            file_stat = {
+                'name': os.path.basename(path),
+                'create_date': time.ctime(os.path.getctime(path)),
+                'edit_date': time.ctime(os.path.getmtime(path)),
+                'size': os.path.getsize(path)
+            }
+            files.append(file_stat)
+    logging.debug(f"Get files from folder {folder}")
+    return files
+
+
+def get_file_data(filename: str) -> dict:
+    """Get full info about file.
+
+    Args:
+        filename (str): Filename.
+
+    Returns:
+        Dict, which contains full info about file. Keys:
+        - name (str): filename
+        - content (str): file content
+        - create_date (datetime): date of file creation
+        - edit_date (datetime): date of last file modification
+        - size (int): size of file in bytes
+
+    Raises:
+        RuntimeError: if file does not exist.
+        ValueError: if filename is invalid.
+    """
+
+    path = get_path(filename)
+    if not is_valid_path(path):
+        raise ValueError(f"Invalid filename {path}")
+
+    if not is_allowed_path(path):
+        raise ValueError(f"Restricted path {path}")
+
+    if not os.path.isfile(path) or not os.path.exists(path):
+        raise RuntimeError(f"RuntimeError: if file does not exist.")
+
+    with open(path, 'r') as file:
+        logging.debug(f"Get files data {path}")
+        return {
+            'name': os.path.basename(path),
+            'create_date': time.ctime(os.path.getctime(path)),
+            'edit_date': time.ctime(os.path.getmtime(path)),
+            'content': file.read(),
+            'size': os.path.getsize(path)
+        }
+
+
+def create_file(filename: str, content: str = None) -> dict:
+    """Create a new file.
+
+    Args:
+        filename (str): Filename.
+        content (str): String with file content.
+
+    Returns:
+        Dict, which contains name of created file. Keys:
+        - name (str): filename
+        - content (str): file content
+        - create_date (datetime): date of file creation
+        - size (int): size of file in bytes
+
+    Raises:
+        ValueError: if filename is invalid.
+    """
+
+    path = get_path(filename)
+    if not is_valid_path(path):
+        raise RuntimeError(f"RuntimeError: if file does not exist.")
+
+    if not is_allowed_path(path):
+        raise ValueError(f"Restricted path {path}")
+
+    if not os.path.exists(filename):
+        logging.warning(f"File already exist {path}")
+
+    with open(filename, 'w') as file:
+        file.write(content)
+
+    return {
+        'name': os.path.basename(path),
+        'create_date': time.ctime(os.path.getatime(path)),
+        'content': content,
+        'size': os.path.getsize(path)
+    }
+
+
+def delete_file(filename: str) -> None:
+    """Delete file.
+
+    Args:
+        filename (str): filename
+
+    Raises:
+        RuntimeError: if file does not exist.
+        ValueError: if filename is invalid.
+    """
+
+    path = get_path(filename)
+    if not is_valid_path(path):
+        raise ValueError(f"Invalid filename {path}")
+
+    if not is_allowed_path(path):
+        raise ValueError(f"Restricted path {path}")
+
+    if not os.path.isfile(path) or not os.path.exists(path):
+        raise RuntimeError(f"RuntimeError: if file does not exist.")
+
+    path = get_path(filename)
+    os.remove(os.path.join(path))
+    logging.debug(f"File removed {path}")
diff --git a/server/__init__.py b/server/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/server/tests/__init__.py b/server/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/server/tests/conftest.py b/server/tests/conftest.py
new file mode 100644
index 0000000..ea9803c
--- /dev/null
+++ b/server/tests/conftest.py
@@ -0,0 +1,33 @@
+import pytest
+import os
+
+
+@pytest.fixture(scope='function')
+def set_default_folder():
+    old_folder = os.getcwd()
+    os.chdir('.\\data')
+    yield
+    os.chdir(old_folder)
+
+
+@pytest.fixture(scope='function')
+def remove_file():
+    yield
+    filepath = os.path.join(os.getcwd(), '0011.txt')
+    if os.path.isfile(filepath) and os.path.exists(filepath):
+        os.remove(filepath)
+
+@pytest.fixture(scope='function')
+def remove_file():
+    yield
+    filepath = os.path.join(os.getcwd(), '0011.txt')
+    if os.path.isfile(filepath) and os.path.exists(filepath):
+        os.remove(filepath)
+
+
+@pytest.fixture(scope='function')
+def create_file():
+    filename = '0011.txt'
+    with open(filename, 'w') as file:
+        file.write('aaa')
+    yield
diff --git a/server/tests/test_FileServer.py b/server/tests/test_FileServer.py
new file mode 100644
index 0000000..dd36c44
--- /dev/null
+++ b/server/tests/test_FileServer.py
@@ -0,0 +1,80 @@
+import os
+from server import FileService
+import pytest
+
+
+class TestChangeDir:
+
+    def test_incorrect_input1(self, set_default_folder):
+        """Pass None as argument
+        """
+        with pytest.raises(TypeError):
+            FileService.change_dir(None)
+
+    def test_incorrect_input2(self, set_default_folder):
+        """Pass .\\1234 as argument
+        """
+
+        old_path = os.getcwd()
+        FileService.change_dir(".\\1234", autocreate=True)
+        assert old_path != os.getcwd()
+
+
+    def test_incorrect_input3(self, set_default_folder):
+        """Pass .\\1234\\1234 as argument
+        """
+
+        with pytest.raises(RuntimeError):
+            FileService.change_dir(".\\1234\\1234", autocreate=False)
+
+    def test_incorrect_input4(self, set_default_folder):
+        """Pass 1235 as argument
+        """
+
+        with pytest.raises(RuntimeError):
+            FileService.change_dir("1235", autocreate=False)
+
+
+class TestGetFiles:
+
+    def test_incorrect_return1(self, set_default_folder):
+        """Pass . as argument
+        """
+
+        return isinstance(FileService.get_files(), list)
+
+
+class TestGetFileData:
+
+    def test_incorrect_input1(self, set_default_folder):
+        with pytest.raises(RuntimeError):
+            FileService.get_file_data("1234.txt")
+
+    def test_incorrect_output(self, set_default_folder):
+        with pytest.raises(ValueError):
+            data = FileService.get_file_data('0011.png')
+            assert ('name', 'create_date', 'edit_date', 'content', 'size') == tuple(data.keys())
+
+    def test_incorrect_input2(self, set_default_folder):
+        with pytest.raises(RuntimeError):
+            FileService.get_file_data('001.png')
+
+
+class TestCreateFile:
+
+    def test_incorrect_output(self, set_default_folder, remove_file):
+        data = FileService.create_file('0011.txt', 'Hello World')
+        assert ('name', 'create_date', 'content', 'size') == tuple(data.keys())
+
+    def test_check_file(self, set_default_folder, remove_file):
+        filename = '0011.txt'
+        FileService.create_file(filename, 'Hello World')
+        assert os.path.isfile(os.path.join(os.getcwd(), filename))
+
+
+class TestDeleteFile:
+
+    def test_delete_file(self, set_default_folder, create_file, remove_file):
+        filename = '0011.txt'
+        FileService.delete_file(filename)
+        assert not os.path.isfile(os.path.join(os.getcwd(), filename))
diff --git a/tasks/02_Add_file_service.md b/tasks/02_Add_file_service.md
new file mode 100644
index 0000000..69bb3c1
--- /dev/null
+++ b/tasks/02_Add_file_service.md
@@ -0,0 +1,14 @@
+
+# Обновление требований
+
+Согласно вашей концепции проекта добавьте реализуемые и желаемые требования в `README.md`
+
+# Реализация слоя работы с файлами и консольного приложения
+
+Для приложения необходимо реализовать:
+
+- Файл `/server/FileService.py`
+  - Все функции модуля `server.FileService`. Используйте библиотеки `os` и `os.path`.
+- Файл `/main.py`
+  - Ключ командной строки `-d folder` для смены текущего каталога.
+- Написать модульные тесты с использованием pytest
\ No newline at end of file