diff --git a/app/calculator.py b/app/calculator.py
index 4f380e8e..668689d3 100644
--- a/app/calculator.py
+++ b/app/calculator.py
@@ -11,6 +11,8 @@ def multiply(x, y):
 
     def divide(x, y):
         if y == 0:
-            return 'Cannot divide by 0'
+            return "Cannot divide by 0"
         return x * 1.0 / y
 
+    def abs(x):
+        return x if x >= 0 else -x
diff --git a/app/test_calculator.py b/app/test_calculator.py
index f5641938..27fa8ef6 100644
--- a/app/test_calculator.py
+++ b/app/test_calculator.py
@@ -8,6 +8,7 @@ def test_add():
     assert Calculator.add(2.0, 0) == 2.0
     assert Calculator.add(-4, 2.0) == -2.0
 
+
 def test_subtract():
     assert Calculator.subtract(1, 2) == -1.0
     assert Calculator.subtract(2, 1) == 1.0
@@ -16,6 +17,7 @@ def test_subtract():
     assert Calculator.subtract(2.0, 0.0) == 2.0
     assert Calculator.subtract(-4, 2.0) == -6.0
 
+
 def test_multiply():
     assert Calculator.multiply(1, 2) == 2.0
     assert Calculator.multiply(1.0, 2.0) == 2.0
@@ -23,9 +25,16 @@ def test_multiply():
     assert Calculator.multiply(2.0, 0.0) == 0.0
     assert Calculator.multiply(-4, 2.0) == -8.0
 
+
 def test_divide():
     # assert Calculator.divide(1, 2) == 0.5
     assert Calculator.divide(1.0, 2.0) == 0.5
     assert Calculator.divide(0, 2.0) == 0
     assert Calculator.divide(-4, 2.0) == -2.0
     # assert Calculator.divide(2.0, 0.0) == 'Cannot divide by 0'
+
+
+def test_abs():
+    assert Calculator.abs(1) == 1
+    assert Calculator.abs(-1) == 1
+    assert Calculator.abs(0) == 0