diff --git a/.gitignore b/.gitignore
index fbac88f4..cfbc8900 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,6 @@ venv
 .DS_STORE
 *.pyc
 .vscode
+assets/
+htmlcov/
+.coverage
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
index 4acbffc0..fa4d8cb0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,7 @@ install:
   - pip install coveralls
 # command to run tests
 script:
+  - pytest
   - coverage run --source=PythonBuddy -m unittest tests/test_linter.py
   - coverage report -m 
   - coveralls
diff --git a/PythonBuddy/app.py b/PythonBuddy/app.py
index 8cee129c..5ab0f7c2 100644
--- a/PythonBuddy/app.py
+++ b/PythonBuddy/app.py
@@ -17,10 +17,10 @@
 from multiprocessing import Pool, cpu_count
 
 
-is_linux = True
-
-if os.name == "nt":
-    is_linux = False
+def is_os_linux():
+    if os.name == "nt":
+        return False
+    return True
 
 # Configure Flask App
 # Remember to change the SECRET_KEY!
@@ -126,7 +126,7 @@ def evaluate_pylint(text):
         for t in text:
             f.write(t)
         f.flush()
-    except Exception as e:
+    except KeyError as e:
         with tempfile.NamedTemporaryFile(delete=False) as temp:
             session["file_name"] = temp.name
             for t in text:
@@ -180,7 +180,7 @@ def process_error(error):
 
     # Detect OS
     line_num = None
-    if is_linux:
+    if is_os_linux():
         try:
             line_num = error.split(":")[1]
         except Exception as e:
@@ -288,11 +288,13 @@ def format_errors(pylint_text):
 #
 #     return "No information at the moment"
 
+def remove_temp_code_file():
+    os.remove(session["file_name"])
 
 @socketio.on('disconnect', namespace='/check_disconnect')
 def disconnect():
     """Remove temp file associated with current session"""
-    os.remove(session["file_name"])
+    remove_temp_code_file()
 
 
 if __name__ == "__main__":
diff --git a/README.md b/README.md
index 1c7dde1f..dba35934 100644
--- a/README.md
+++ b/README.md
@@ -92,8 +92,13 @@ This is still in alpha stage so there might be some bugs. If you want to impleme
 ### Unit Tests
 To run tests, run this at the root directory:
 ```
-python -m tests.test_linter
+pytest
 ```
+For coverage run the following command in the root directory:
+```
+pytest --cov-report html --cov=PythonBuddy tests/
+```
+
 
 ### Future Goals:
 - Make easily embeddable for MOOCs like edX and other education platform
diff --git a/requirements.txt b/requirements.txt
index 7e03c211..4e5ed667 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -19,3 +19,6 @@ six==1.11.0
 typed-ast==1.1.0
 Werkzeug==0.15.3
 wrapt==1.10.11
+pytest==5.2.1
+pytest-cov==2.8.1
+pytest-html==2.0.0
diff --git a/tests/test_app.py b/tests/test_app.py
new file mode 100644
index 00000000..2b459986
--- /dev/null
+++ b/tests/test_app.py
@@ -0,0 +1,128 @@
+from datetime import datetime
+import flask
+import unittest
+from unittest.mock import patch
+from PythonBuddy.app import *
+from os import path
+
+
+class TestIndexPage(unittest.TestCase):
+    def test_index(self):
+        """Test the index page that it is displayed
+        :param self: instance of the current test.
+        """
+        test_client = app.test_client()
+        index_page = test_client.get('/')
+        self.assertEqual(index_page.status, '200 OK')
+        self.assertTrue(b'Python Linter Online' in index_page.data)
+
+    def test_index_session(self):
+        """Test the flask session on the index page.
+        :param self: instance of the current test.
+        """
+        with app.test_client() as test_client:
+            index_page = test_client.get('/')
+
+            self.assertTrue('count' in flask.session)
+            self.assertTrue('time_now' in flask.session)
+
+
+class TestUtilities(unittest.TestCase):
+    @patch('PythonBuddy.app.os')
+    def test_is_os_linux(self, os_name_patch):
+        """Test the linux check in the PythonBuddy app
+        :param self: instance of the current test.
+        :param os_name_patch: patch of the os in the pybuddy app
+        """
+        os_name_patch.name = "nt"
+        self.assertFalse(is_os_linux())
+
+        os_name_patch.name = "ubuntu :)"
+        self.assertTrue(is_os_linux())
+
+
+class TestCodeRunning(unittest.TestCase):
+    def setUp(self):
+        self.code_example = "for i in range(5):\n    print(i)\n"
+        self.code_example_modified = "print(\"Oh hai Mark\")"
+        self.error_message = [
+            {
+                "code": self.code_example,
+                "error": "",
+                "message": "",
+                "line": "",
+                "error_info": "",
+            }
+        ]
+
+    @patch('PythonBuddy.app.evaluate_pylint')
+    def test_check_code_endpoint_no_evaluate_pylint(self, evaluate_pytlint_patch):
+        """Test the check code endpoint
+        :param self: instance of the current test.
+        :param evaluate_pytlint_patch: patch of the os in the evaluate_pytlint
+            testing this separately.
+        """
+        evaluate_pytlint_patch.return_value = self.error_message
+        with app.test_client() as test_client:
+            check_code_page = test_client.post('/check_code', data={
+                    "text": self.code_example
+                })
+            self.assertEqual(check_code_page.status, '200 OK')
+            self.assertTrue('code' in flask.session)
+            self.assertEqual(flask.session['code'], self.code_example)
+
+    @patch('PythonBuddy.app.slow')
+    def test_run_code_slow(self, slow_patch):
+        """Test that when code is running too much
+        :param self: instance of current test
+        :param slow_patch: path the slow method, test separately
+        """
+        slow_patch.return_value = True
+        test_client = app.test_client()
+        check_run_code = test_client.post('/run_code', data={})
+        self.assertEqual(check_run_code.status, '200 OK')
+        self.assertTrue(b"Running code too much" in check_run_code.data)
+
+    def test_evaluate_pylint_test_file_creation_deletion_and_contents(self):
+        """Test the evaluate pylint method in depth.
+        :param self: instance of the current test.
+
+        first check if the file will get created (keyerror thrown)
+        second check if code in file will get modified
+        """
+        with app.test_client() as test_client:
+            test_client.get('/') # this will set the count
+            test_client.post('/check_code', data={
+                "text": self.code_example
+            })
+
+            # first test
+            # this will check that the exception is raised and
+            # a new file is created
+            test_client.post('/run_code')
+            self.assertTrue('file_name' in flask.session)
+
+            # this will check that the exception is raised and
+            # a new file is created
+            test_client.post('/check_code', data={
+                "text": self.code_example_modified
+            })
+            # check the code is modified
+            temp_code_file = open(flask.session['file_name'], "r")
+            self.assertEqual(temp_code_file.read(), self.code_example_modified)
+
+    def test_if_file_created_and_deleted(self):
+        """Test if the file will get created and deleted.
+        :param self: instance of the current test.
+        """
+        with app.test_client() as test_client:
+
+            test_client.post('/check_code', data={
+                "text": self.code_example
+            })
+            # check if the file still exists
+            self.assertTrue(path.exists(flask.session['file_name']))
+            remove_temp_code_file()
+
+            # ensure file is deleted
+            self.assertFalse(path.exists(flask.session['file_name']))
diff --git a/tests/test_linter.py b/tests/test_linter.py
index 72d53d35..44e046b7 100644
--- a/tests/test_linter.py
+++ b/tests/test_linter.py
@@ -22,7 +22,6 @@ def test_process_error(self):
         self.assertEqual(process_error(None), None)
         self.assertEqual(process_error(""), None)
 
-
     def test_no_errors(self):
         """ Asserts format_errors function returns None when
         
@@ -36,8 +35,5 @@ def test_no_errors(self):
             None
         )
 
-
-
 if __name__ == '__main__':
-    # print(process_error("s"))
     unittest.main()