diff --git a/participants/scipy_002/pr_tutorial/simple_functions.py b/participants/scipy_002/pr_tutorial/simple_functions.py
index c3dcf8f..f9caaa6 100644
--- a/participants/scipy_002/pr_tutorial/simple_functions.py
+++ b/participants/scipy_002/pr_tutorial/simple_functions.py
@@ -10,3 +10,17 @@ def factorial(value):
         return 1
     else:
         return value * factorial(value - 1)
+
+def is_prime(value):
+    if value < 2:
+        raise ValueError(f"Don't pass any numbers smaller than 2. Received {value}.")
+    elif value == 2:
+        return True
+    
+    current_val = 2
+    while current_val < value:
+        if value % current_val == 0:
+            return False
+        
+        current_val += 1
+    return True
\ No newline at end of file
diff --git a/participants/scipy_002/pr_tutorial/tests/test_simple_function.py b/participants/scipy_002/pr_tutorial/tests/test_simple_function.py
index 1982130..662bcc8 100644
--- a/participants/scipy_002/pr_tutorial/tests/test_simple_function.py
+++ b/participants/scipy_002/pr_tutorial/tests/test_simple_function.py
@@ -1,7 +1,29 @@
-from pr_tutorial.simple_functions import factorial
-
+from pr_tutorial.simple_functions import factorial, is_prime
 
 def test_factorial_3():
     """Simplest test for one crete case"""
 
     assert factorial(3) == 6
+
+def test_is_prime():
+    """Simple test for naive is_prime() function."""
+    primes_below_100 = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 
+                        41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 
+                        89, 97]
+    
+    for num in range(1, 100):
+        if num == 1:
+            try:
+                is_prime(num)
+            except ValueError as e:
+                continue
+            except Exception as e: # wrong exception raised
+                assert False
+            assert False
+        else:
+            primeOrNot = is_prime(num)
+
+            if num in primes_below_100:
+                assert primeOrNot is True
+            else:
+                assert primeOrNot is False       
\ No newline at end of file