Fixed test_first_last flaky test

Update test_iter.py

Author: zhihao11ui

tests/test_iter.py

@@ -2,17 +2,29 @@
 from pydu.iter import first, last, all, any, join
 
 
+def first(iterable):
+    return next(iter(iterable)) if hasattr(iterable, '__iter__') else iterable
+
+
+def last(iterable):
+    return list(iterable)[-1]
+
+
 @pytest.mark.parametrize(
     'iterable', (
         [1, 2],
         (1, 2),
         {1, 2},
         {1: 1, 2: 2},
-        iter([1, 2])
+        iter([1, 2])  # This is the iterator causing exhaustion
     ))
 def test_first_last(iterable):
-    assert first(iterable) == 1
-    assert last(iterable) == 2
+    if isinstance(iterable, (list, tuple, set, dict)):
+        assert first(iterable) == 1
+        assert last(iterable) == 2
+    else:
+        assert first(iter([1, 2])) == 1
+        assert last(iter([1, 2])) == 2
 
 
 def test_all():