add tests

test_leap_year.py

@@ -0,0 +1,20 @@
+import pytest
+
+from leap_year.leap_year import is_leap_year
+
+
+@pytest.mark.parametrize("year,flag", [
+        (1896, True),
+        (1900, False),
+        (1904, True),
+
+        (1996, True),
+        (2000, True),
+        (2004, True),
+
+        (2096, True),
+        (2100, False),
+        (2104, True),
+])
+def test_leap_years(year, flag):
+    assert flag == is_leap_year(year)

tox.ini

@@ -1,5 +1,10 @@
 [tox]
-envlist = flake8
+envlist = py35,flake8
+
+
+[testenv]
+deps = pytest
+commands = pytest test_leap_year.py
 
 
 [testenv:flake8]