Accept single dtype in dh.resut_type() and thus ph.assert_dtype()

Author: honno

array_api_tests/dtype_helpers.py

@@ -151,9 +151,11 @@ class MinMax(NamedTuple):
 }
 
 
-def result_type(*dtypes):
-    if len(dtypes) < 2:
+def result_type(*dtypes: DataType):
+    if len(dtypes) == 0:
         raise ValueError()
+    elif len(dtypes) == 1:
+        return dtypes[0]
     result = promotion_table[dtypes[0], dtypes[1]]
     for i in range(2, len(dtypes)):
         result = promotion_table[result, dtypes[i]]

array_api_tests/meta_tests/test_pytest_helpers.py

@@ -0,0 +1,13 @@
+from pytest import raises
+
+from .. import pytest_helpers as ph
+from .. import _array_module as xp
+
+
+def test_assert_dtype():
+    ph.assert_dtype("promoted_func", (xp.uint8, xp.int8), xp.int16)
+    with raises(AssertionError):
+        ph.assert_dtype("bad_func", (xp.uint8, xp.int8), xp.float32)
+    ph.assert_dtype("bool_func", (xp.uint8, xp.int8), xp.bool, xp.bool)
+    ph.assert_dtype("single_promoted_func", (xp.uint8,), xp.uint8)
+    ph.assert_dtype("single_bool_func", (xp.uint8,), xp.bool, xp.bool)