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import { expect } from 'chai';import { SinonFakeTimers, SinonStub, stub, useFakeTimers } from 'sinon';import { promisify } from 'util';import { ConsecutiveBreaker } from './breaker/Breaker';import { CircuitBreakerPolicy, CircuitState } from './CircuitBreakerPolicy';import { abortedSignal } from './common/abort';import { BrokenCircuitError, TaskCancelledError } from './errors/Errors';import { IsolatedCircuitError } from './errors/IsolatedCircuitError';import { circuitBreaker, handleAll, handleType } from './Policy';
class MyException extends Error {}
const delay = promisify(setTimeout);
describe('CircuitBreakerPolicy', () => {  let p: CircuitBreakerPolicy;  let clock: SinonFakeTimers;  let onBreak: SinonStub;  let onReset: SinonStub;  let onHalfOpen: SinonStub;
  beforeEach(() => {    p = circuitBreaker(handleType(MyException), {      halfOpenAfter: 1000,      breaker: new ConsecutiveBreaker(2),    });    clock = useFakeTimers();    onBreak = stub();    onReset = stub();    onHalfOpen = stub();    p.onBreak(onBreak);    p.onReset(onReset);    p.onHalfOpen(onHalfOpen);  });
  afterEach(() => {    clock.restore();  });
  const openBreaker = async () => {    const s = stub().throws(new MyException());    await expect(p.execute(s)).to.be.rejectedWith(MyException);    await expect(p.execute(s)).to.be.rejectedWith(MyException);  };
  it('allows calls when open', async () => {    expect(await p.execute(() => 42)).to.equal(42);  });
  it('opens after failing calls', async () => {    const s = stub().throws(new MyException());
    await expect(p.execute(s)).to.be.rejectedWith(MyException);    expect(p.state).to.equal(CircuitState.Closed);    expect(onBreak).not.called;
    await expect(p.execute(s)).to.be.rejectedWith(MyException);    expect(p.state).to.equal(CircuitState.Open);    expect(onBreak).called;
    await expect(p.execute(s)).to.be.rejectedWith(BrokenCircuitError);    expect(p.state).to.equal(CircuitState.Open);
    expect((p.lastFailure as any).error).to.be.an.instanceOf(MyException);    expect(onBreak).calledOnce;    expect(s).calledTwice;  });
  it('closes if the half open test succeeds', async () => {    await openBreaker();
    clock.tick(1000);
    const result = p.execute(stub().resolves(42));    expect(p.state).to.equal(CircuitState.HalfOpen);    expect(onHalfOpen).calledOnce;    expect(await result).to.equal(42);    expect(p.state).to.equal(CircuitState.Closed);    expect(onReset).calledOnce;  });
  it('dedupes half-open tests', async () => {    await openBreaker();    clock.tick(1000);
    // Two functinos, a and b. We execute with "a" first, and then make sure    // it returns before "b" gets called.    let aReturned = false;    const a = async () => {      await delay(10);      aReturned = true;      return 1;    };
    const b = async () => {      expect(aReturned).to.be.true;      return 2;    };
    const todo = [      expect(p.execute(a)).to.eventually.equal(1),      expect(p.execute(b)).to.eventually.equal(2),    ];
    clock.tick(10);
    await Promise.all(todo);  });
  it('stops deduped half-open tests if the circuit reopens', async () => {    await openBreaker();    clock.tick(1000);
    // Two functinos, a and b. We execute with "a" first, and then make sure    // it returns before "b" gets called.    const a = async () => {      await delay(10);      throw new MyException();    };
    const b = async () => {      throw new Error('expected to not be called');    };
    const todo = [      expect(p.execute(a)).to.be.rejectedWith(MyException),      expect(p.execute(b)).to.be.rejectedWith(BrokenCircuitError),    ];
    clock.tick(10);
    await Promise.all(todo);  });
  it('re-opens if the half open fails', async () => {    await openBreaker();
    clock.tick(1000);
    const s = stub().throws(new MyException());    await expect(p.execute(s)).to.be.rejectedWith(MyException);    expect(p.state).to.equal(CircuitState.Open);  });
  it('handles isolation correctly', async () => {    const handle1 = p.isolate();    expect(onBreak).calledOnceWith({ isolated: true });
    const handle2 = p.isolate();    expect(onBreak).calledOnce;
    expect(p.state).to.equal(CircuitState.Isolated);    await expect(p.execute(() => 42)).to.be.rejectedWith(IsolatedCircuitError);
    handle1.dispose();    expect(p.state).to.equal(CircuitState.Isolated);    expect(onReset).not.called;
    handle2.dispose();    expect(p.state).to.equal(CircuitState.Closed);    expect(onReset).calledOnce;
    expect(await p.execute(() => 42)).to.equal(42);  });
  it('links parent cancellation token', async () => {    const parent = new AbortController();    await circuitBreaker(handleAll, {      halfOpenAfter: 1000,      breaker: new ConsecutiveBreaker(3),    }).execute(({ signal }) => {      expect(signal.aborted).to.be.false;      parent.abort();      expect(signal.aborted).to.be.true;    }, parent.signal);  });
  it('aborts function execution if half open test succeeds', async () => {    await openBreaker();
    clock.tick(1000);
    // half open test:    p.execute(stub().resolves(42));
    // queued timeout:    await expect(p.execute(stub(), abortedSignal)).to.be.rejectedWith(TaskCancelledError);
    expect(p.state).to.equal(CircuitState.Closed);    expect(onReset).calledOnce;  });});