TST: Test squeeze with CoW

pandas/tests/copy_view/test_methods.py

@@ -634,3 +634,22 @@ def test_droplevel(using_copy_on_write):
 
     assert not np.shares_memory(get_array(df2, "c"), get_array(df, "c"))
     tm.assert_frame_equal(df, df_orig)
+
+
+def test_squeeze(using_copy_on_write):
+    df = DataFrame({"a": [1, 2, 3]})
+    df_orig = df.copy()
+    series = df.squeeze()
+
+    # Should share memory regardless of CoW since squeeze is just an iloc
+    assert np.shares_memory(series.values, get_array(df, "a"))
+
+    # mutating squeezed df triggers a copy-on-write for that column/block
+    series.iloc[0] = 0
+    if using_copy_on_write:
+        assert not np.shares_memory(series.values, get_array(df, "a"))
+        tm.assert_frame_equal(df, df_orig)
+    else:
+        # Without CoW the original will be modified
+        assert np.shares_memory(series.values, get_array(df, "a"))
+        assert df.loc[0, "a"] == 0