TST: Old issues

pandas/tests/apply/test_series_apply.py

@@ -878,3 +878,15 @@ def test_apply_dictlike_transformer(string_series, ops):
         expected.name = string_series.name
         result = string_series.apply(ops)
         tm.assert_series_equal(result, expected)
+
+
+def test_apply_retains_column_name():
+    # GH 16380
+    df = DataFrame({"x": range(3)}, Index(range(3), name="x"))
+    result = df.x.apply(lambda x: Series(range(x + 1), Index(range(x + 1), name="y")))
+    expected = DataFrame(
+        [[0.0, np.nan, np.nan], [0.0, 1.0, np.nan], [0.0, 1.0, 2.0]],
+        columns=Index(range(3), name="y"),
+        index=Index(range(3), name="x"),
+    )
+    tm.assert_frame_equal(result, expected)

pandas/tests/arithmetic/test_categorical.py

@@ -13,3 +13,13 @@ def test_categorical_nan_equality(self):
         expected = Series([True, True, True, False])
         result = cat == cat
         tm.assert_series_equal(result, expected)
+
+    def test_categorical_tuple_equality(self):
+        # GH 18050
+        ser = Series([(0, 0), (0, 1), (0, 0), (1, 0), (1, 1)])
+        expected = Series([True, False, True, False, False])
+        result = ser == (0, 0)
+        tm.assert_series_equal(result, expected)
+
+        result = ser.astype("category") == (0, 0)
+        tm.assert_series_equal(result, expected)

pandas/tests/frame/test_stack_unstack.py

@@ -2081,3 +2081,21 @@ def test_unstack_categorical_columns(self):
         )
         expected.columns = MultiIndex.from_tuples([("cat", 0), ("cat", 1)])
         tm.assert_frame_equal(result, expected)
+
+    def test_stack_unsorted(self):
+        # GH 16925
+        PAE = ["ITA", "FRA"]
+        VAR = ["A1", "A2"]
+        TYP = ["CRT", "DBT", "NET"]
+        MI = MultiIndex.from_product([PAE, VAR, TYP], names=["PAE", "VAR", "TYP"])
+
+        V = list(range(len(MI)))
+        DF = DataFrame(data=V, index=MI, columns=["VALUE"])
+
+        DF = DF.unstack(["VAR", "TYP"])
+        DF.columns = DF.columns.droplevel(0)
+        DF.loc[:, ("A0", "NET")] = 9999
+
+        result = DF.stack(["VAR", "TYP"]).sort_index()
+        expected = DF.sort_index(axis=1).stack(["VAR", "TYP"]).sort_index()
+        tm.assert_series_equal(result, expected)

pandas/tests/groupby/test_function.py

@@ -1155,3 +1155,13 @@ def test_groupby_sum_below_mincount_nullable_integer():
     result = grouped.sum(min_count=2)
     expected = DataFrame({"b": [pd.NA] * 3, "c": [pd.NA] * 3}, dtype="Int64", index=idx)
     tm.assert_frame_equal(result, expected)
+
+
+def test_mean_on_timedelta():
+    # GH 17382
+    df = DataFrame({"time": pd.to_timedelta(range(10)), "cat": ["A", "B"] * 5})
+    result = df.groupby("cat")["time"].mean()
+    expected = Series(
+        pd.to_timedelta([4, 5]), name="time", index=Index(["A", "B"], name="cat")
+    )
+    tm.assert_series_equal(result, expected)

pandas/tests/groupby/test_rank.py

@@ -648,3 +648,16 @@ def test_groupby_axis0_cummax_axis1():
     expected = df[[0, 1]].astype(np.float64)
     expected[2] = expected[1]
     tm.assert_frame_equal(cmax, expected)
+
+
+def test_non_unique_index():
+    # GH 16577
+    df = DataFrame(
+        {"A": [1.0, 2.0, 3.0, np.nan], "value": 1.0},
+        index=[pd.Timestamp("20170101", tz="US/Eastern")] * 4,
+    )
+    result = df.groupby([df.index, "A"]).value.rank(ascending=True, pct=True)
+    expected = Series(
+        [1.0] * 4, index=[pd.Timestamp("20170101", tz="US/Eastern")] * 4, name="value"
+    )
+    tm.assert_series_equal(result, expected)

pandas/tests/groupby/transform/test_transform.py

@@ -1289,3 +1289,11 @@ def test_transform_cumcount():
 
     result = grp.transform("cumcount")
     tm.assert_series_equal(result, expected)
+
+
+def test_null_group_lambda_self():
+    # GH 17093
+    df = DataFrame({"A": [1, np.nan], "B": [1, 1]})
+    result = df.groupby("A").transform(lambda x: x)
+    expected = DataFrame([1], columns=["B"])
+    tm.assert_frame_equal(result, expected)

pandas/tests/io/parser/test_read_fwf.py

@@ -853,3 +853,12 @@ def test_len_colspecs_len_names_with_index_col(
         index_col=index_col,
     )
     tm.assert_frame_equal(result, expected)
+
+
+def test_colspecs_with_comment():
+    # GH 14135
+    result = read_fwf(
+        StringIO("#\nA1K\n"), colspecs=[(1, 2), (2, 3)], comment="#", header=None
+    )
+    expected = DataFrame([[1, "K"]], columns=[0, 1])
+    tm.assert_frame_equal(result, expected)