Much more thorough tests! (#1053)

src/random.ts

@@ -0,0 +1,18 @@
+import { Random } from "roughjs/bin/math";
+import nanoid from "nanoid";
+
+let random = new Random(Date.now());
+let testIdBase = 0;
+
+export function randomInteger() {
+  return Math.floor(random.next() * 2 ** 31);
+}
+
+export function reseed(seed: number) {
+  random = new Random(seed);
+  testIdBase = 0;
+}
+
+export function randomId() {
+  return process.env.NODE_ENV === "test" ? `id${testIdBase++}` : nanoid();
+}