rsxjs/__tests__/integration/breaker/test-from-sync.js

Resilience Extensions for JS.

/**
 * @file tests/breaker/test-from-sync.js
 * @copyright 2018-present Karim Alibhai. All rights reserved.
 */

import { test } from "../../helpers";
import lolex from "lolex";

import { Breaker } from "../../../";

test("Breaker.fromSync()", (t) => {
  const MAX_ERRORS = 1; // trip after one error
  const TIMEOUT = 500; // wait for 500 seconds in between states

  let shouldThrowError = false;
  let nCalls = 0;

  const breakerFn = Breaker.fromSync(
    () => {
      ++nCalls;

      if (shouldThrowError) {
        throw new Error("Failure!");
      }

      return Math.PI;
    },
    {
      maxErrors: MAX_ERRORS,
      timeout: TIMEOUT,
    }
  );

  const clock = lolex.install({
    target: global,
    toFake: ["Date"],
  });

  // to start, should not throw error
  t.is(breakerFn(), Math.PI);
  t.is(nCalls, 1);

  // throw real error now
  shouldThrowError = true;
  t.is(t.throws(breakerFn).message, "Failure!");
  t.is(nCalls, 2);

  // should still throw error now that breaker is tripped
  shouldThrowError = false;
  t.is(t.throws(breakerFn).message, "Failure!");
  // still only called twice, breaker has been tripped
  t.is(nCalls, 2);

  // should call function again after timeout (half-open)
  clock.tick(TIMEOUT + 1);
  shouldThrowError = true;
  t.is(t.throws(breakerFn).message, "Failure!");
  t.is(nCalls, 3, "should have run a third time");

  // breaker should be tripped again
  shouldThrowError = false;
  t.is(t.throws(breakerFn).message, "Failure!");
  t.is(nCalls, 3);

  // breaker should be half-open again
  clock.tick(TIMEOUT);
  t.is(breakerFn(), Math.PI);
  t.is(nCalls, 4);

  // breaker should be open again
  t.is(breakerFn(), Math.PI);
  t.is(nCalls, 5);

  // cleanup
  clock.uninstall();
});