add throw test for complete file

test/unit-files.cpp

@@ -43,6 +43,12 @@ TEST_CASE("complete-files") {
             CHECK(env.render_file_with_json_file(test_name + "/template.txt", test_name + "/data.json") == env.load_file(test_name + "/result.txt"));
         }
     }
+
+    for (std::string test_name : {"error-unknown"}) {
+        SUBCASE(test_name.c_str()) {
+            CHECK_THROWS_WITH(env.render_file_with_json_file(test_name + "/template.txt", test_name + "/data.json"), "[inja.exception.parser_error] (at 2:11) expected 'in', got 'ins'");
+        }
+    }
 }
 
 TEST_CASE("complete-files-whitespace-control") {