Adds a test to modify writable flag

Author: oleksandr-pavlyk

dpctl/tests/test_usm_ndarray_ctor.py

@@ -57,6 +57,7 @@ def test_allocate_usm_ndarray(shape, usm_type):
 
 
 def test_usm_ndarray_flags():
+    get_queue_or_skip()
     assert dpt.usm_ndarray((5,), dtype="i4").flags.fc
     assert dpt.usm_ndarray((5, 2), dtype="i4").flags.c_contiguous
     assert dpt.usm_ndarray((5, 2), dtype="i4", order="F").flags.f_contiguous
@@ -68,6 +69,17 @@ def test_usm_ndarray_flags():
         (5, 1, 2), dtype="i4", strides=(1, 0, 5)
     ).flags.f_contiguous
     assert dpt.usm_ndarray((5, 1, 1), dtype="i4", strides=(1, 0, 1)).flags.fc
+    x = dpt.empty(5, dtype="u2")
+    assert x.flags.writable is True
+    x.flags.writable = False
+    assert x.flags.writable is False
+    with pytest.raises(ValueError):
+        x[:] = 0
+    x.flags["W"] = True
+    assert x.flags.writable is True
+    x.flags["WRITABLE"] = True
+    assert x.flags.writable is True
+    x[:] = 0
 
 
 @pytest.mark.parametrize(