From 6f947ce7e9967fb2237783e793973e71fc39189b Mon Sep 17 00:00:00 2001
From: Florian Pfaff <6773539+FlorianPfaff@users.noreply.github.com>
Date: Sat, 27 Jun 2026 10:08:52 +0200
Subject: [PATCH 1/5] No-op test update


From 6a82e319fb9f7775767d1b4f3699e6642a374912 Mon Sep 17 00:00:00 2001
From: Florian Pfaff <6773539+FlorianPfaff@users.noreply.github.com>
Date: Sat, 27 Jun 2026 10:09:25 +0200
Subject: [PATCH 2/5] Validate Autograd multinomial probabilities

---
 src/pyrecest/_backend/autograd/random.py | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/pyrecest/_backend/autograd/random.py b/src/pyrecest/_backend/autograd/random.py
index f1ada7402..261164cec 100644
--- a/src/pyrecest/_backend/autograd/random.py
+++ b/src/pyrecest/_backend/autograd/random.py
@@ -1,6 +1,22 @@
 """Autograd based random backend."""
 
 import autograd.numpy as _np
-from autograd.numpy.random import get_state, multinomial, randint, seed, set_state
+from autograd.numpy.random import get_state, randint, seed, set_state
+from autograd.numpy.random import multinomial as _autograd_multinomial
 
 from .._shared_numpy.random import choice, multivariate_normal, normal, rand, uniform
+
+
+def _validate_multinomial_pvals(pvals):
+    try:
+        pvals_array = _np.asarray(pvals)
+    except (TypeError, ValueError) as exc:
+        raise TypeError("pvals must be real numeric") from exc
+    if pvals_array.dtype.kind not in "iuf":
+        raise TypeError("pvals must be real numeric")
+    return pvals_array
+
+
+def multinomial(n, pvals, size=None):
+    pvals_array = _validate_multinomial_pvals(pvals)
+    return _autograd_multinomial(n, pvals_array, size=size)

From e9020287820453331e9de5bcee90a4663953d55c Mon Sep 17 00:00:00 2001
From: Florian Pfaff <6773539+FlorianPfaff@users.noreply.github.com>
Date: Sat, 27 Jun 2026 10:09:49 +0200
Subject: [PATCH 3/5] Add Autograd random backend test scaffold

---
 tests/backend/test_autograd_random_backend.py | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 tests/backend/test_autograd_random_backend.py

diff --git a/tests/backend/test_autograd_random_backend.py b/tests/backend/test_autograd_random_backend.py
new file mode 100644
index 000000000..51d3a674e
--- /dev/null
+++ b/tests/backend/test_autograd_random_backend.py
@@ -0,0 +1,9 @@
+import pytest
+
+pytest.importorskip("autograd")
+
+from pyrecest._backend.autograd import random  # noqa: E402
+
+
+def test_autograd_random_backend_imports():
+    assert random is not None

From 4711743cecae1f864d9b5444b515d3cda73e0417 Mon Sep 17 00:00:00 2001
From: Florian Pfaff <6773539+FlorianPfaff@users.noreply.github.com>
Date: Sat, 27 Jun 2026 10:10:13 +0200
Subject: [PATCH 4/5] Add Autograd multinomial smoke test

---
 tests/backend/test_autograd_random_backend.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tests/backend/test_autograd_random_backend.py b/tests/backend/test_autograd_random_backend.py
index 51d3a674e..06d322e44 100644
--- a/tests/backend/test_autograd_random_backend.py
+++ b/tests/backend/test_autograd_random_backend.py
@@ -1,3 +1,4 @@
+import numpy as np
 import pytest
 
 pytest.importorskip("autograd")
@@ -5,5 +6,9 @@
 from pyrecest._backend.autograd import random  # noqa: E402
 
 
-def test_autograd_random_backend_imports():
-    assert random is not None
+def test_multinomial_accepts_real_probability_values():
+    draw = getattr(random, "multinomial")
+    sample = draw(4, [0.25, 0.75])
+
+    assert sample.shape == (2,)
+    assert int(np.sum(sample)) == 4

From 9d4ca368c0a00ea983f705e1984c2376f6c5874d Mon Sep 17 00:00:00 2001
From: Florian Pfaff <6773539+FlorianPfaff@users.noreply.github.com>
Date: Sat, 27 Jun 2026 10:10:43 +0200
Subject: [PATCH 5/5] Cover Autograd multinomial probability validation

---
 tests/backend/test_autograd_random_backend.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/backend/test_autograd_random_backend.py b/tests/backend/test_autograd_random_backend.py
index 06d322e44..79a399d2e 100644
--- a/tests/backend/test_autograd_random_backend.py
+++ b/tests/backend/test_autograd_random_backend.py
@@ -12,3 +12,11 @@ def test_multinomial_accepts_real_probability_values():
 
     assert sample.shape == (2,)
     assert int(np.sum(sample)) == 4
+
+
+def test_multinomial_rejects_non_numeric_dtype_probability_values():
+    draw = getattr(random, "multinomial")
+    pvals = np.array([1, 0], dtype="?")
+
+    with pytest.raises(TypeError, match="real numeric"):
+        draw(4, pvals)