add test for iter.first and iter.last

tests/test_iter.py

@@ -0,0 +1,15 @@
+import pytest
+from pydu.iter import first, last
+
+
+@pytest.mark.parametrize(
+    'iterable', (
+        [1, 2],
+        (1, 2),
+        {1, 2},
+        {1: 1, 2: 2},
+        iter([1, 2])
+    ))
+def test_first_last(iterable):
+    assert first(iterable) == 1
+    assert last(iterable) == 2