From f010612905bfffd4a9eada3ec1c6937017716a3a Mon Sep 17 00:00:00 2001
From: ajpotts <ajpotts@users.noreply.github.com>
Date: Tue, 6 Jan 2026 15:51:23 -0500
Subject: [PATCH] Closes #5242:  alignment tests for arkouda.numpy.char

---
 pytest.ini                                    |  1 +
 .../alignment_verification/char_alignment.py  | 99 +++++++++++++++++++
 2 files changed, 100 insertions(+)
 create mode 100644 tests/numpy/alignment_verification/char_alignment.py

diff --git a/pytest.ini b/pytest.ini
index dbd4e226daa..eba9d81551a 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -51,6 +51,7 @@ testpaths =
     tests/numpy/dtypes_test.py
     tests/numpy/err_test.py
     tests/numpy/manipulation_functions_test.py
+    tests/numpy/alignment_verification/char_alignment.py
     tests/numpy/alignment_verification/operators_alignment.py
     tests/numpy/numeric_test.py
     tests/numpy/numpy_test.py
diff --git a/tests/numpy/alignment_verification/char_alignment.py b/tests/numpy/alignment_verification/char_alignment.py
new file mode 100644
index 00000000000..41109b658b4
--- /dev/null
+++ b/tests/numpy/alignment_verification/char_alignment.py
@@ -0,0 +1,99 @@
+import random
+import string
+
+import numpy as np
+import pytest
+
+import arkouda as ak
+import arkouda.numpy.char as ak_char
+
+
+def _np_isnumeric(py_list: list[str]) -> np.ndarray:
+    """
+    NumPy alignment target:
+    np.char.isnumeric applies Python's str.isnumeric elementwise.
+    """
+    a = np.array(py_list, dtype=str)
+    return np.char.isnumeric(a)
+
+
+class TestArkoudaNumpyCharAlignment:
+    def test_public_api_reexports_match_numpy(self):
+        # These should be exactly the NumPy objects re-exported
+        assert ak_char.bool_ is np.bool_
+        assert ak_char.int_ is np.int_
+        assert ak_char.integer is np.integer
+        assert ak_char.object_ is np.object_
+        assert ak_char.str_ is np.str_
+        assert ak_char.character is np.character
+
+        # Ensure isnumeric exists and is callable
+        assert callable(ak_char.isnumeric)
+
+    def test_isnumeric_rejects_non_strings(self):
+        with pytest.raises(TypeError, match=r"input to isnumeric must be Strings"):
+            ak_char.isnumeric(ak.arange(3))
+
+        with pytest.raises(TypeError, match=r"input to isnumeric must be Strings"):
+            ak_char.isnumeric(["1", "2", "3"])
+
+    @pytest.mark.xfail(
+        reason="Known mismatch: empty string treated as numeric in Arkouda "
+        "(should be False like NumPy). Issue #5243"
+    )
+    @pytest.mark.parametrize(
+        "py_list",
+        [
+            ["Strings 0", "Strings 1", "Strings 2", "120", "121", "122"],
+            ["", "0", "00", "  ", "3.14", "-1", "+2", "１２３", "٣", "二"],  # noqa: RUF001
+            ["1e3", "⅕", "²", "₇", "2³₇", "2³x₇", "٣٤٥", "१२३"],
+        ],
+    )
+    def test_isnumeric_matches_numpy_char(self, py_list):
+        s = ak.array(py_list)
+
+        got = ak_char.isnumeric(s).to_ndarray()
+        exp = _np_isnumeric(py_list)
+
+        assert got.dtype == np.bool_
+        np.testing.assert_array_equal(got, exp)
+
+    def test_isnumeric_unicode_special_examples_from_docstring(self):
+        py_list = ["3.14", "\u0030", "\u00b2", "2³₇", "2³x₇"]
+        s = ak.array(py_list)
+
+        got = ak_char.isnumeric(s).to_ndarray()
+        exp = _np_isnumeric(py_list)
+
+        np.testing.assert_array_equal(got, exp)
+
+    @pytest.mark.xfail(
+        reason="Known mismatch: empty string treated as numeric in Arkouda "
+        "(should be False like NumPy). Issue #5243"
+    )
+    def test_isnumeric_randomized_matches_python_and_numpy(self):
+        # Keep this deterministic and cheap
+        rng = random.Random(0)
+
+        # Build strings from digits, letters, punctuation, whitespace,
+        # plus a few unicode numeric characters.
+        unicode_numerics = ["²", "³", "₇", "⅕", "٣", "१२३", "１２３"]  # noqa: RUF001
+        alphabet = string.digits + string.ascii_letters + string.punctuation + " \t"
+
+        py_list: list[str] = []
+        for _ in range(200):
+            if rng.random() < 0.15:
+                py_list.append(rng.choice(unicode_numerics))
+                continue
+            n = rng.randint(0, 12)
+            py_list.append("".join(rng.choice(alphabet) for _ in range(n)))
+
+        s = ak.array(py_list)
+        got = ak_char.isnumeric(s).to_ndarray()
+
+        # Primary truth: Python's str.isnumeric elementwise
+        py_truth = np.array([x.isnumeric() for x in py_list], dtype=np.bool_)
+        np.testing.assert_array_equal(got, py_truth)
+
+        # Secondary cross-check: NumPy's char implementation
+        np.testing.assert_array_equal(got, _np_isnumeric(py_list))