anchor/tests/events/tests/events.js

const anchor = require("@project-serum/anchor");
const { assert } = require("chai");

describe("events", () => {
  // Configure the client to use the local cluster.
  anchor.setProvider(anchor.AnchorProvider.env());
  const program = anchor.workspace.Events;

  it("Is initialized!", async () => {
    let listener = null;

    let [event, slot] = await new Promise((resolve, _reject) => {
      listener = program.addEventListener("MyEvent", (event, slot) => {
        resolve([event, slot]);
      });
      program.rpc.initialize();
    });
    await program.removeEventListener(listener);

    assert.isAbove(slot, 0);
    assert.strictEqual(event.data.toNumber(), 5);
    assert.strictEqual(event.label, "hello");
  });

  it("Multiple events", async () => {
    // Sleep so we don't get this transaction has already been processed.
    await sleep(2000);

    let listenerOne = null;
    let listenerTwo = null;

    let [eventOne, slotOne] = await new Promise((resolve, _reject) => {
      listenerOne = program.addEventListener("MyEvent", (event, slot) => {
        resolve([event, slot]);
      });
      program.rpc.initialize();
    });

    let [eventTwo, slotTwo] = await new Promise((resolve, _reject) => {
      listenerTwo = program.addEventListener("MyOtherEvent", (event, slot) => {
        resolve([event, slot]);
      });
      program.rpc.testEvent();
    });

    await program.removeEventListener(listenerOne);
    await program.removeEventListener(listenerTwo);

    assert.isAbove(slotOne, 0);
    assert.strictEqual(eventOne.data.toNumber(), 5);
    assert.strictEqual(eventOne.label, "hello");

    assert.isAbove(slotTwo, 0);
    assert.strictEqual(eventTwo.data.toNumber(), 6);
    assert.strictEqual(eventTwo.label, "bye");
  });
});

function sleep(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}