Add tests for calculate_mean

foo/tests/test_bar.py

@@ -3,7 +3,7 @@
 # Filename: test_bar.py
 from unittest import TestCase
 
-from foo.bar import whats_the_meaning_of_life
+from foo.bar import whats_the_meaning_of_life, calculate_mean
 
 __author__ = "Your Name"
 __credits__ = []
@@ -20,3 +20,21 @@ class TestMeaningOfLife(TestCase):
 
     def test_meaning_of_life_with_one_core(self):
         assert 42 == whats_the_meaning_of_life(n_cores=1)
+
+
+class TestCalculateMean(TestCase):
+    """Tests for the calculate_mean function"""
+
+    def test_calculate_mean_of_a_single_number_returns_the_number_itself(self):
+        assert 0 == calculate_mean([0])
+        assert 1 == calculate_mean([1])
+        assert 2 == calculate_mean([2])
+        assert -1 == calculate_mean([-1])
+        assert 1.5 == calculate_mean([1.5])
+
+    def test_calculate_mean_returns_mean_of_a_list_of_numbers(self):
+        assert 2 == calculate_mean([1, 2, 3])
+        assert 3 == calculate_mean([1, 2, 3, 4, 5])
+
+    def test_calculate_mean_returns_correct_value_for_negative_numbers(self):
+        assert -3 == calculate_mean([-1, -2, -3, -4, -5])