Improve enum validation test cases for decimal values

Author: vai-mikkoleppanen

src/validators/literal.rs

@@ -182,7 +182,7 @@ impl<T: Debug> LiteralLookup<T> {
             return Ok(None);
         };
 
-        if py_input.is_instance(get_decimal_type(py)).is_err() {
+        if let Ok(false) = py_input.is_instance(get_decimal_type(py)) {
             return Ok(None);
         }
 

tests/validators/test_enums.py

@@ -377,3 +377,6 @@ class MyEnum(Enum):
     )
     with pytest.raises(ValidationError):
         v.validate_python(Decimal(2))
+
+    with pytest.raises(ValidationError):
+        v.validate_python((1, 2))