refactor common test helpers into test/

This way we can share them with multiple tests

src/utils/index.ts

@@ -21,18 +21,3 @@ export function assert(condition: boolean, message: string): void {
 export function hex(n: number, pad: number): string {
     return `0x${n.toString(16).padStart(pad, '0')}`;
 }
-
-/**
- * Looks up a nested property in an object.
- * @param obj The object
- * @param id The property path
- */
-export function lookup(obj: object, id: string): string | undefined {
-    const value = id
-        .split('.')
-        .reduce((pv, cv) => pv && (pv as Record<string, object>)[cv], obj);
-    if (typeof value === 'string') {
-        return value;
-    }
-    return undefined;
-}