diff --git a/.codecov.yml b/.codecov.yml
new file mode 100644
index 0000000..c3da9d8
--- /dev/null
+++ b/.codecov.yml
@@ -0,0 +1,13 @@
+codecov:
+  require_ci_to_pass: yes
+
+coverage:
+  precision: 1
+  round: down
+  target: "20...100"
+
+ignore:
+  - '**/test/**'
+  - 'env/**'
+  - 'reports/**'
+  - '.pytest_cache/**'
diff --git a/.github/workflows/continous_integration.yml b/.github/workflows/continous_integration.yml
index 33caf8c..ba6f1d4 100644
--- a/.github/workflows/continous_integration.yml
+++ b/.github/workflows/continous_integration.yml
@@ -1,14 +1,30 @@
 name: Python application
 
-on: [push]
+on: [push,pull_request]
 
 jobs:
   build:
 
+    env:
+      PYTHON_FILES: .
+
     runs-on: ubuntu-latest
 
     steps:
     - uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - name: get changed files for push
+      if: ${{ github.event_name == 'push' }}
+      run: |
+        echo ::set-env name=PYTHON_FILES::$(find . -type f -name "*.py" | xargs git diff --name-only --diff-filter=ACMRT ${{ github.sha }}~ ${{ github.sha }} | awk '{print $1}' | paste -d' ' -s)
+    - name: get changed files for pull request
+      if: ${{ github.event_name == 'pull_request' }}
+      run: |
+        echo ::set-env name=PYTHON_FILES::$(find . -type f -name "*.py" | xargs git diff --name-only --diff-filter=ACMRT origin/${{ github.base_ref }} origin/${{ github.head_ref }} | awk '{print $1}' | paste -d' ' -s)
+    - name: print PYTHON_FILES
+      run: |
+        echo ${{ env.PYTHON_FILES }}
     - name: Set up Python 3.8
       uses: actions/setup-python@v1
       with:
@@ -17,21 +33,18 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r requirements.txt
-    - name: get changed files
-      id: getfile
-      run: |
-        echo "::set-output name=files::$(git diff-tree --no-commit-id --name-only -r ${{ github.sha }} | xargs)"
-    - name: echo output
+    - name: Formatting check
+      if: ${{ env.PYTHON_FILES }}
       run: |
-        echo ${{ steps.getfile.outputs.files }}
-#    - name: Lint with flake8
-#      run: |
-#        pip install -q wemake-python-styleguide
-#        wget "https://raw.githubusercontent.com/ebot7/eb7-styleguide/master/settings/setup_ml_githooks.cfg"
-#        flake8 pgb/ --config=setup_ml_githooks.cfg
-#        rm setup_ml_githooks.cfg
-#      with:
-#        - fail_ci_if_error: true
+        pip install -qU autoflake==1.4 black==20.8b1 docformatter==1.3.1 isort==5.5.3
+        echo "Checking with autoflake"
+        autoflake --check --expand-star-imports --remove-all-unused-imports --ignore-init-module-imports --remove-duplicate-keys --remove-unused-variables ${{ env.PYTHON_FILES }}
+        echo "Checking with docformatter"
+        docformatter --check --make-summary-multi-line --pre-summary-newline ${{ env.PYTHON_FILES }}
+        echo "Checking with isort"
+        isort --check-only --quiet ${{ env.PYTHON_FILES }}
+        echo "Checking with black"
+        black --check ${{ env.PYTHON_FILES }} -l 79
     - name: Test with pytest
       run: |
         pip install pytest==5.3.5 coverage==4.5.4
diff --git a/pgb/add.py b/pgb/add.py
index 74b7093..c98172c 100644
--- a/pgb/add.py
+++ b/pgb/add.py
@@ -1,6 +1,6 @@
 def add(a: int, b: int) -> int:
     """
-    Adds two number
+    Adds two number.
 
     Args:
         a (int): First argument
diff --git a/pgb/mul.py b/pgb/mul.py
index 8b4d21b..bb11a46 100644
--- a/pgb/mul.py
+++ b/pgb/mul.py
@@ -1,6 +1,6 @@
 def mul(a: int, b: int) -> int:
     """
-    Multiplies two number
+    Multiplies two number.
 
     Args:
         a (int): First argument
diff --git a/pgb/pow.py b/pgb/pow.py
new file mode 100644
index 0000000..595f3ac
--- /dev/null
+++ b/pgb/pow.py
@@ -0,0 +1,12 @@
+def pow(a: int, b: int) -> int:
+    """
+    Power of two number.
+
+    Args:
+        a (int): First argument
+        b (int): Second argument
+
+    Returns:
+        Power of second arguments on the base of first argument
+    """
+    return a ** b
diff --git a/pgb/sub.py b/pgb/sub.py
index 2ad8680..9a467f0 100644
--- a/pgb/sub.py
+++ b/pgb/sub.py
@@ -1,6 +1,6 @@
 def sub(a: int, b: int) -> int:
     """
-    Subtracts two number
+    Subtracts two number.
 
     Args:
         a (int): First argument
diff --git a/tests/test_calculator.py b/tests/test_calculator.py
index 39d0781..2c3f613 100644
--- a/tests/test_calculator.py
+++ b/tests/test_calculator.py
@@ -1,5 +1,6 @@
 import unittest
-from pgb import add, mul
+
+from pgb import add, mul, pow, sub
 
 
 class TestCalculator(unittest.TestCase):
@@ -13,6 +14,16 @@ def test_mul(self):
         b = 10
         self.assertEqual(mul.mul(a, b), 50)
 
+    def test_sub(self):
+        a = 5
+        b = 10
+        self.assertEqual(sub.sub(a, b), -5)
+
+    def test_pow(self):
+        a = 2
+        b = 10
+        self.assertEqual(pow.pow(a, b), 1024)
+
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     unittest.main()