move test helpers from demo app to tests/

demo/static/tests/helpers/index.ts

@@ -1,11 +1,6 @@
 export { MockRouter } from "./mock_router";
 export { MockServer } from "./mock_server";
 export { makeMenuInfo, makeTestData, TestData } from "./test_data";
-export { makeTestEnv, makeTestWEnv, TestEnv, TestInfo } from "./test_env";
-export {
-  makeDeferred,
-  makeTestFixture,
-  nextMicroTick,
-  nextTick,
-  normalize
-} from "./test_utils";
+export { makeTestEnv, TestEnv, TestInfo } from "./test_env";
+
+export * from "../../../../tests/helpers";