test: add test

tests/test_2793_nep_70_gradual_support.py

@@ -1,4 +1,5 @@
 # BSD 3-Clause License; see https://github.com/scikit-hep/awkward-1.0/blob/main/LICENSE
+import contextlib
 
 import numpy as np
 import packaging.version
@@ -11,22 +12,30 @@
 )
 
 
-@pytest.mark.skipif(NUMPY_HAS_NEP_50, reason="NEP-50 requires NumPy >= 1.24.0")
-def test_with_nep_50():
-    array = ak.from_numpy(np.arange(255, dtype=np.uint8))
+@pytest.mark.skipif(not NUMPY_HAS_NEP_50, reason="NEP-50 requires NumPy >= 1.24.0")
+@pytest.mark.parametrize("backend", ["cpu", "typetracer"])
+def test_with_nep_50(backend):
+    array = ak.to_backend(np.arange(255, dtype=np.uint8), backend)
     assert array.layout.dtype == np.dtype(np.uint8)
 
     typed_scalar = np.uint64(0)
     assert (array + typed_scalar).layout.dtype == np.dtype(np.uint64)
 
     # With NEP-50, we can ask NumPy to use value-less type resolution
-    untyped_scalar = 512
-    assert (array + untyped_scalar).layout.dtype == np.dtype(np.uint8)
-
-
-@pytest.mark.skipif(not NUMPY_HAS_NEP_50, reason="NumPy >= 1.24.0 has NEP-50 support")
-def test_without_nep_50():
-    array = ak.from_numpy(np.arange(255, dtype=np.uint8))
+    warn_context = (
+        pytest.warns(DeprecationWarning, match="out-of-bound Python integers")
+        if backend == "cpu"
+        else contextlib.nullcontext()
+    )
+    with warn_context:
+        untyped_scalar = 512
+        assert (array + untyped_scalar).layout.dtype == np.dtype(np.uint8)
+
+
+@pytest.mark.skipif(NUMPY_HAS_NEP_50, reason="NumPy >= 1.24.0 has NEP-50 support")
+@pytest.mark.parametrize("backend", ["cpu", "typetracer"])
+def test_without_nep_50(backend):
+    array = ak.to_backend(np.arange(255, dtype=np.uint8), backend)
     assert array.layout.dtype == np.dtype(np.uint8)
 
     # Without NEP-50, we still don't drop type information for typed-scalars,