TST: Add droplevel tests for corner cases

Author: toobaz

pandas/tests/indexes/test_base.py

@@ -245,6 +245,20 @@ def test_constructor_int_dtype_nan(self):
         result = Index(data, dtype='float')
         tm.assert_index_equal(result, expected)
 
+    def test_droplevel(self):
+        # GH 21115
+        index = Index([0, 1, 2, 3], name='only')
+
+        assert index.droplevel([]).equals(index)
+
+        for level in 'only', ['only']:
+            with pytest.raises(ValueError):
+                index.droplevel(level)
+
+        for level in 'wrong', ['wrong']:
+            with pytest.raises(KeyError):
+                index.droplevel(level)
+
     @pytest.mark.parametrize("dtype", ['int64', 'uint64'])
     def test_constructor_int_dtype_nan_raises(self, dtype):
         # see gh-15187

pandas/tests/indexes/test_multi.py

@@ -2078,7 +2078,7 @@ def test_droplevel_with_names(self):
         expected = index.droplevel(1)
         assert dropped.equals(expected)
 
-    def test_droplevel_multiple(self):
+    def test_droplevel_list(self):
         index = MultiIndex(
             levels=[Index(lrange(4)), Index(lrange(4)), Index(lrange(4))],
             labels=[np.array([0, 0, 1, 2, 2, 2, 3, 3]), np.array(
@@ -2089,6 +2089,16 @@ def test_droplevel_multiple(self):
         expected = index[:2].droplevel(2).droplevel(0)
         assert dropped.equals(expected)
 
+        dropped = index[:2].droplevel([])
+        expected = index[:2]
+        assert dropped.equals(expected)
+
+        with pytest.raises(ValueError):
+            index[:2].droplevel(['one', 'two', 'three'])
+
+        with pytest.raises(KeyError):
+            index[:2].droplevel(['one', 'four'])
+
     def test_drop_not_lexsorted(self):
         # GH 12078