refactor: separate elements logic into a standalone package (#9285)

packages/common/tests/queue.test.ts

@@ -0,0 +1,62 @@
+import { Queue } from "../src/queue";
+
+describe("Queue", () => {
+  const calls: any[] = [];
+
+  const createJobFactory =
+    <T>(
+      // for purpose of this test, Error object will become a rejection value
+      resolutionOrRejectionValue: T,
+      ms = 1,
+    ) =>
+    () => {
+      return new Promise<T>((resolve, reject) => {
+        setTimeout(() => {
+          if (resolutionOrRejectionValue instanceof Error) {
+            reject(resolutionOrRejectionValue);
+          } else {
+            resolve(resolutionOrRejectionValue);
+          }
+        }, ms);
+      }).then((x) => {
+        calls.push(x);
+        return x;
+      });
+    };
+
+  beforeEach(() => {
+    calls.length = 0;
+  });
+
+  it("should await and resolve values in order of enqueueing", async () => {
+    const queue = new Queue();
+
+    const p1 = queue.push(createJobFactory("A", 50));
+    const p2 = queue.push(createJobFactory("B"));
+    const p3 = queue.push(createJobFactory("C"));
+
+    expect(await p3).toBe("C");
+    expect(await p2).toBe("B");
+    expect(await p1).toBe("A");
+
+    expect(calls).toEqual(["A", "B", "C"]);
+  });
+
+  it("should reject a job if it throws, and not affect other jobs", async () => {
+    const queue = new Queue();
+
+    const err = new Error("B");
+
+    queue.push(createJobFactory("A", 50));
+    const p2 = queue.push(createJobFactory(err));
+    const p3 = queue.push(createJobFactory("C"));
+
+    const p2err = p2.catch((err) => err);
+
+    await p3;
+
+    expect(await p2err).toBe(err);
+
+    expect(calls).toEqual(["A", "C"]);
+  });
+});