call check_backend_support directly from backend fixture (#3666)

diff --git a/tests/test_utils.py b/tests/test_utils.py
index 2b5a2af..a1fa80b 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -32,10 +32,9 @@
     supported = pretend.stub(
         kwargs={"only_if": lambda backend: False, "skip_message": "Nope"}
     )
-    item = pretend.stub(keywords={"supported": [supported]},
-                        funcargs={"backend": True})
+    item = pretend.stub(keywords={"supported": [supported]})
     with pytest.raises(pytest.skip.Exception) as exc_info:
-        check_backend_support(item)
+        check_backend_support(True, item)
     assert exc_info.value.args[0] == "Nope (True)"
 
 
@@ -43,19 +42,8 @@
     supported = pretend.stub(
         kwargs={"only_if": lambda backend: True, "skip_message": "Nope"}
     )
-    item = pretend.stub(keywords={"supported": [supported]},
-                        funcargs={"backend": True})
-    assert check_backend_support(item) is None
-
-
-def test_check_backend_support_no_backend():
-    supported = pretend.stub(
-        kwargs={"only_if": "notalambda", "skip_message": "Nope"}
-    )
-    item = pretend.stub(keywords={"supported": supported},
-                        funcargs={})
-    with pytest.raises(ValueError):
-        check_backend_support(item)
+    item = pretend.stub(keywords={"supported": [supported]})
+    assert check_backend_support(None, item) is None
 
 
 def test_load_nist_vectors():