diff --git a/.github/workflows/python-app.yml b/.github/workflows/python-app.yml
new file mode 100644
index 0000000..7981386
--- /dev/null
+++ b/.github/workflows/python-app.yml
@@ -0,0 +1,40 @@
+# This workflow will install Python dependencies, run tests and lint with a single version of Python
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python
+
+name: Python application
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Python 3.10
+      uses: actions/setup-python@v3
+      with:
+        python-version: "3.10"
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install flake8 pytest
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+    - name: Lint with flake8
+      run: |
+        # stop the build if there are Python syntax errors or undefined names
+        flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+        # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
+        flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+    - name: Test with pytest
+      run: |
+        cd test
+        pytest test_testing.py
diff --git a/.gitignore b/.gitignore
index 550d67d..5371a01 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-src/__pycache__
+*/__pycache__
+.vscode
\ No newline at end of file
diff --git a/heatpathcal.py b/heatpathcal.py
index 6879a4a..da8f2d6 100644
--- a/heatpathcal.py
+++ b/heatpathcal.py
@@ -1,6 +1,6 @@
 import argparse, os, sys
-sys.path.append(os.path.abspath(str(os.getcwd())+"/src"))
-import fileio, calculation
+sys.path.append("./src")
+import calculation, fileio
 
 #command line parsing
 Parser=argparse.ArgumentParser(description="Calculates the total resistance for given heat paths")
diff --git a/info/input_file_guideline.md b/info/input_file_guideline.md
index 721fd17..a40648a 100644
--- a/info/input_file_guideline.md
+++ b/info/input_file_guideline.md
@@ -14,4 +14,4 @@ If a heat path *travels through multiple paths*, keep them **on the same row**:\
 
 **If no length was given**, by default, **use 1**.
 
-For example files, please look in the [test directory](../test/) in this repository.
\ No newline at end of file
+For example files, please look in the [sample directory](../sample/) in this repository.
\ No newline at end of file
diff --git a/test/high/battery_support_bracket_to_panel.csv b/sample/high/battery_support_bracket_to_panel.csv
similarity index 100%
rename from test/high/battery_support_bracket_to_panel.csv
rename to sample/high/battery_support_bracket_to_panel.csv
diff --git a/test/high/negz_xy_panels.csv b/sample/high/negz_xy_panels.csv
similarity index 100%
rename from test/high/negz_xy_panels.csv
rename to sample/high/negz_xy_panels.csv
diff --git a/test/high/rail_to_xy_panel.csv b/sample/high/rail_to_xy_panel.csv
similarity index 100%
rename from test/high/rail_to_xy_panel.csv
rename to sample/high/rail_to_xy_panel.csv
diff --git a/test/low/battery_top_bracket_to_eps.csv b/sample/low/battery_top_bracket_to_eps.csv
similarity index 100%
rename from test/low/battery_top_bracket_to_eps.csv
rename to sample/low/battery_top_bracket_to_eps.csv
diff --git a/src/__init__.py b/src/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/formula.py b/src/formula.py
index 0c621cc..b047eb8 100644
--- a/src/formula.py
+++ b/src/formula.py
@@ -5,16 +5,18 @@
 May also be used to calculate contact resistance
 """
 def rec_cs(k, A, L = 1):
-  return L/(k*A)
+  if (L == 0):
+    return abs(1/(k*A))
+  return abs(L/(k*A))
 
 """
 Compute material resistance for cylindrical cross section
 """
 def cyl_cs(k, r1, r2, L):
-  return (log(r1/r2))/(2*pi*L*k)
+  return abs((log(r1/r2))/(2*pi*L*k))
 
 """
 Compute material resistance for sphereical object
 """
 def sph(k, r1, r2):
-  return (r2-r1)/(4*pi*r2*r1*k)
+  return abs((r2-r1)/(4*pi*r2*r1*k))
diff --git a/test/test_testing.py b/test/test_testing.py
new file mode 100644
index 0000000..878205e
--- /dev/null
+++ b/test/test_testing.py
@@ -0,0 +1,15 @@
+import sys
+sys.path.append("../src")
+import calculation, fileio, formula, structure
+
+def test_rec_cs_regular():
+    assert formula.rec_cs(3, 5, 0.5) == 1/30
+
+def test_rec_cs_nothird():
+    assert formula.rec_cs(3, 5) == 1/15
+
+def test_rec_cs_zero():
+    assert formula.rec_cs(3, 5, 0) == 1/15
+
+def test_rec_cs_negative():
+    assert formula.rec_cs(3, -5, 0.5) == 1/30
\ No newline at end of file