fix deprecation test

src/pyhepmc/_deprecated.py

@@ -9,6 +9,7 @@
 
 class deprecated:
     def __init__(self, reason: str, removal: str = ""):
+        assert isinstance(reason, str)
         self.reason = reason
         self.removal = Version(removal) if removal else None
 

tests/test_deprecated.py

@@ -7,15 +7,25 @@ class Foo:
     def bar(self):
         return 0
 
+    @deprecated("use baz", removal="1000.0.0")
+    def foo(self):
+        return 0
+
 
 def test_deprecated():
     foo = Foo()
 
-    with pytest.raises(ValueError, match="reason.*required"):
+    with pytest.raises(AssertionError):
 
         @deprecated
         def bad(self):
             return 0
 
     with pytest.warns(DeprecationWarning, match="bar is deprecated: use baz"):
         foo.bar()
+
+    with pytest.warns(
+        FutureWarning,
+        match="bar is deprecated and will be removed in version 1000.0.0: use baz",
+    ):
+        foo.foo()