update indexing tests with new behaviour to get them passing

pandas/core/internals/array_manager.py

@@ -378,6 +378,7 @@ def where(self: T, other, cond, align: bool, errors: str) -> T:
     #     return self.apply_with_block("setitem", indexer=indexer, value=value)
 
     def putmask(self, mask, new, align: bool = True):
+        # TODO(CoW) check references to copy if needed
         if align:
             align_keys = ["new", "mask"]
         else:

pandas/tests/indexes/period/test_period.py

@@ -255,16 +255,20 @@ def test_is_(self):
         assert not index.is_(index - 2)
         assert not index.is_(index - 0)
 
-    def test_index_duplicate_periods(self):
+    def test_index_duplicate_periods(self, using_array_manager):
         # monotonic
         idx = PeriodIndex([2000, 2007, 2007, 2009, 2009], freq="A-JUN")
         ts = Series(np.random.randn(len(idx)), index=idx)
+        original = ts.copy()
 
         result = ts["2007"]
         expected = ts[1:3]
         tm.assert_series_equal(result, expected)
         result[:] = 1
-        assert (ts[1:3] == 1).all()
+        if using_array_manager:
+            tm.assert_series_equal(ts, original)
+        else:
+            assert (ts[1:3] == 1).all()
 
         # not monotonic
         idx = PeriodIndex([2000, 2007, 2007, 2009, 2007], freq="A-JUN")

pandas/tests/indexing/multiindex/test_chaining_and_caching.py

@@ -12,6 +12,7 @@
 import pandas.core.common as com
 
 
+@td.skip_array_manager_not_yet_implemented
 def test_detect_chained_assignment():
     # Inplace ops, originally from:
     # https://stackoverflow.com/questions/20508968/series-fillna-in-a-multiindex-dataframe-does-not-fill-is-this-a-bug

pandas/tests/indexing/multiindex/test_setitem.py

@@ -390,16 +390,24 @@ def test_setitem_change_dtype(self, multiindex_dataframe_random_data):
         reindexed = dft.reindex(columns=[("foo", "two")])
         tm.assert_series_equal(reindexed["foo", "two"], s > s.median())
 
-    def test_set_column_scalar_with_loc(self, multiindex_dataframe_random_data):
+    def test_set_column_scalar_with_loc(
+        self, multiindex_dataframe_random_data, using_array_manager
+    ):
         frame = multiindex_dataframe_random_data
         subset = frame.index[[1, 4, 5]]
 
         frame.loc[subset] = 99
         assert (frame.loc[subset].values == 99).all()
 
+        frame_original = frame.copy()
+
         col = frame["B"]
         col[subset] = 97
-        assert (frame.loc[subset, "B"] == 97).all()
+        if using_array_manager:
+            # chained setitem doesn't work with CoW
+            tm.assert_frame_equal(frame, frame_original)
+        else:
+            assert (frame.loc[subset, "B"] == 97).all()
 
     def test_nonunique_assignment_1750(self):
         df = DataFrame(
@@ -472,21 +480,31 @@ def test_frame_setitem_view_direct(multiindex_dataframe_random_data):
     assert (df["foo"].values == 0).all()
 
 
-def test_frame_setitem_copy_raises(multiindex_dataframe_random_data):
+def test_frame_setitem_copy_raises(
+    multiindex_dataframe_random_data, using_array_manager
+):
     # will raise/warn as its chained assignment
     df = multiindex_dataframe_random_data.T
-    msg = "A value is trying to be set on a copy of a slice from a DataFrame"
-    with pytest.raises(com.SettingWithCopyError, match=msg):
+    if using_array_manager:
+        # TODO(CoW) it would be nice if this could still warn/raise
         df["foo"]["one"] = 2
+    else:
+        msg = "A value is trying to be set on a copy of a slice from a DataFrame"
+        with pytest.raises(com.SettingWithCopyError, match=msg):
+            df["foo"]["one"] = 2
 
 
-def test_frame_setitem_copy_no_write(multiindex_dataframe_random_data):
+def test_frame_setitem_copy_no_write(
+    multiindex_dataframe_random_data, using_array_manager
+):
     frame = multiindex_dataframe_random_data.T
     expected = frame
     df = frame.copy()
-    msg = "A value is trying to be set on a copy of a slice from a DataFrame"
-    with pytest.raises(com.SettingWithCopyError, match=msg):
+    if using_array_manager:
         df["foo"]["one"] = 2
+    else:
+        msg = "A value is trying to be set on a copy of a slice from a DataFrame"
+        with pytest.raises(com.SettingWithCopyError, match=msg):
+            df["foo"]["one"] = 2
 
-    result = df
-    tm.assert_frame_equal(result, expected)
+    tm.assert_frame_equal(df, expected)