TST: Add tests for clip with CoW (#51492)

Author: phofl

pandas/tests/copy_view/test_clip.py

@@ -19,3 +19,54 @@ def test_clip_inplace_reference(using_copy_on_write):
         assert df._mgr._has_no_reference(0)
         assert view._mgr._has_no_reference(0)
         tm.assert_frame_equal(df_copy, view)
+
+
+def test_clip_inplace_reference_no_op(using_copy_on_write):
+    df = DataFrame({"a": [1.5, 2, 3]})
+    df_copy = df.copy()
+    arr_a = get_array(df, "a")
+    view = df[:]
+    df.clip(lower=0, inplace=True)
+
+    if using_copy_on_write:
+        assert np.shares_memory(get_array(df, "a"), arr_a)
+        assert not df._mgr._has_no_reference(0)
+        assert not view._mgr._has_no_reference(0)
+        tm.assert_frame_equal(df_copy, view)
+    else:
+        assert not np.shares_memory(get_array(df, "a"), arr_a)
+
+
+def test_clip_inplace(using_copy_on_write):
+    df = DataFrame({"a": [1.5, 2, 3]})
+    arr_a = get_array(df, "a")
+    df.clip(lower=2, inplace=True)
+
+    # Clip not actually inplace right now but could be
+    assert not np.shares_memory(get_array(df, "a"), arr_a)
+
+    if using_copy_on_write:
+        assert df._mgr._has_no_reference(0)
+
+
+def test_clip(using_copy_on_write):
+    df = DataFrame({"a": [1.5, 2, 3]})
+    df_orig = df.copy()
+    df2 = df.clip(lower=2)
+
+    assert not np.shares_memory(get_array(df2, "a"), get_array(df, "a"))
+
+    if using_copy_on_write:
+        assert df._mgr._has_no_reference(0)
+    tm.assert_frame_equal(df_orig, df)
+
+
+def test_clip_no_op(using_copy_on_write):
+    df = DataFrame({"a": [1.5, 2, 3]})
+    df2 = df.clip(lower=0)
+
+    if using_copy_on_write:
+        assert not df._mgr._has_no_reference(0)
+        assert np.shares_memory(get_array(df2, "a"), get_array(df, "a"))
+    else:
+        assert not np.shares_memory(get_array(df2, "a"), get_array(df, "a"))