chore: Improve error message when a schema has no "Query" type

Author: Stranger6667

src/hypothesis_graphql/_strategies/queries.py

@@ -8,7 +8,7 @@
 def query(schema: str) -> st.SearchStrategy:
     parsed_schema = graphql.build_schema(schema)
     if parsed_schema.query_type is None:
-        raise ValueError
+        raise ValueError("Query type is not defined in the schema")
     return get_strategy_for_type(parsed_schema.query_type).map(make_query).map(graphql.print_ast)
 
 

test/test_queries.py

@@ -1,4 +1,5 @@
 import graphql
+import pytest
 from hypothesis import given
 
 import hypothesis_graphql.strategies as gql_st
@@ -26,3 +27,11 @@ def test(query):
         graphql.parse(query)
 
     test()
+
+
+def test_missing_query():
+    schema = """type Author {
+      name: String
+    }"""
+    with pytest.raises(ValueError, match="Query type is not defined in the schema"):
+        gql_st.query(schema)