add helpers test

castero/helpers.py

@@ -1,6 +1,3 @@
-import os
-
-
 def third(n) -> int:
     """Calculates one-third of a given value.
 

tests/test_helpers.py

@@ -0,0 +1,40 @@
+from castero import helpers
+
+
+def test_third_zero():
+    result = helpers.third(0)
+    assert result == 0
+
+
+def test_third_basic():
+    result = helpers.third(3)
+    assert result == 1
+
+
+def test_third_indivisible():
+    result = helpers.third(4)
+    assert result == 1
+
+
+def test_median_empty():
+    values = []
+    result = helpers.median(values)
+    assert result is None
+
+
+def test_median_1():
+    values = [1]
+    result = helpers.median(values)
+    assert result == 1
+
+
+def test_median_2():
+    values = [1, 3]
+    result = helpers.median(values)
+    assert result == 2
+
+
+def test_median_3():
+    values = [1, 2, 3]
+    result = helpers.median(values)
+    assert result == 2