TST: Add more tests for fixed issues (#30674)

Author: mroeschke

pandas/tests/groupby/test_nth.py

@@ -89,6 +89,25 @@ def test_first_last_nth_dtypes(df_mixed_floats):
     assert f.dtype == "int64"
 
 
+def test_first_strings_timestamps():
+    # GH 11244
+    test = pd.DataFrame(
+        {
+            pd.Timestamp("2012-01-01 00:00:00"): ["a", "b"],
+            pd.Timestamp("2012-01-02 00:00:00"): ["c", "d"],
+            "name": ["e", "e"],
+            "aaaa": ["f", "g"],
+        }
+    )
+    result = test.groupby("name").first()
+    expected = DataFrame(
+        [["a", "c", "f"]],
+        columns=Index([Timestamp("2012-01-01"), Timestamp("2012-01-02"), "aaaa"]),
+        index=Index(["e"], name="name"),
+    )
+    tm.assert_frame_equal(result, expected)
+
+
 def test_nth():
     df = DataFrame([[1, np.nan], [1, 4], [5, 6]], columns=["A", "B"])
     g = df.groupby("A")

pandas/tests/io/parser/test_c_parser_only.py

@@ -597,3 +597,14 @@ def test_file_binary_mode(c_parser_only):
         with open(path, "rb") as f:
             result = parser.read_csv(f, header=None)
             tm.assert_frame_equal(result, expected)
+
+
+def test_unix_style_breaks(c_parser_only):
+    # GH 11020
+    parser = c_parser_only
+    with tm.ensure_clean() as path:
+        with open(path, "w", newline="\n") as f:
+            f.write("blah\n\ncol_1,col_2,col_3\n\n")
+        result = parser.read_csv(path, skiprows=2, encoding="utf-8", engine="c")
+    expected = DataFrame(columns=["col_1", "col_2", "col_3"])
+    tm.assert_frame_equal(result, expected)

pandas/tests/test_multilevel.py

@@ -1359,6 +1359,30 @@ def test_mixed_depth_drop(self):
         )
         tm.assert_frame_equal(expected, result)
 
+    def test_drop_multiindex_other_level_nan(self):
+        # GH 12754
+        df = (
+            DataFrame(
+                {
+                    "A": ["one", "one", "two", "two"],
+                    "B": [np.nan, 0.0, 1.0, 2.0],
+                    "C": ["a", "b", "c", "c"],
+                    "D": [1, 2, 3, 4],
+                }
+            )
+            .set_index(["A", "B", "C"])
+            .sort_index()
+        )
+        result = df.drop("c", level="C")
+        expected = DataFrame(
+            [2, 1],
+            columns=["D"],
+            index=pd.MultiIndex.from_tuples(
+                [("one", 0.0, "b"), ("one", np.nan, "a")], names=["A", "B", "C"]
+            ),
+        )
+        tm.assert_frame_equal(result, expected)
+
     def test_drop_nonunique(self):
         df = DataFrame(
             [
@@ -2286,6 +2310,14 @@ def test_sort_index_and_reconstruction_doc_example(self):
 
         tm.assert_frame_equal(result, expected)
 
+    def test_sort_index_non_existent_label_multiindex(self):
+        # GH 12261
+        df = DataFrame(0, columns=[], index=pd.MultiIndex.from_product([[], []]))
+        df.loc["b", "2"] = 1
+        df.loc["a", "3"] = 1
+        result = df.sort_index().index.is_monotonic
+        assert result is True
+
     def test_sort_index_reorder_on_ops(self):
         # 15687
         df = DataFrame(