sinon-chai.js

export default function (chai, utils) {
  const slice = Array.prototype.slice;

  function isSpy(putativeSpy) {
    return (
      typeof putativeSpy === 'function' &&
      typeof putativeSpy.getCall === 'function' &&
      typeof putativeSpy.calledWithExactly === 'function'
    );
  }

  function timesInWords(count) {
    switch (count) {
      case 1: {
        return 'once';
      }
      case 2: {
        return 'twice';
      }
      case 3: {
        return 'thrice';
      }
      default: {
        return (count || 0) + ' times';
      }
    }
  }

  function isCall(putativeCall) {
    return putativeCall && isSpy(putativeCall.proxy);
  }

  function assertCanWorkWith(assertion) {
    if (!isSpy(assertion._obj) && !isCall(assertion._obj)) {
      throw new TypeError(
        utils.inspect(assertion._obj) + ' is not a spy or a call to a spy!'
      );
    }
  }

  function getMessages(spy, action, nonNegatedSuffix, always, args) {
    var verbPhrase = always ? 'always have ' : 'have ';
    nonNegatedSuffix = nonNegatedSuffix || '';
    if (isSpy(spy.proxy)) {
      spy = spy.proxy;
    }

    function printfArray(array) {
      return spy.printf.apply(spy, array);
    }

    return {
      affirmative: function () {
        return printfArray(
          ['expected %n to ' + verbPhrase + action + nonNegatedSuffix].concat(
            args
          )
        );
      },
      negative: function () {
        return printfArray(
          ['expected %n to not ' + verbPhrase + action].concat(args)
        );
      }
    };
  }

  function sinonProperty(name, action, nonNegatedSuffix) {
    utils.addProperty(chai.Assertion.prototype, name, function () {
      assertCanWorkWith(this);

      var messages = getMessages(this._obj, action, nonNegatedSuffix, false);
      this.assert(this._obj[name], messages.affirmative, messages.negative);
    });
  }

  function sinonPropertyAsBooleanMethod(name, action, nonNegatedSuffix) {
    utils.addMethod(chai.Assertion.prototype, name, function (arg) {
      assertCanWorkWith(this);

      var messages = getMessages(this._obj, action, nonNegatedSuffix, false, [
        timesInWords(arg)
      ]);
      this.assert(
        this._obj[name] === arg,
        messages.affirmative,
        messages.negative
      );
    });
  }

  function createSinonMethodHandler(sinonName, action, nonNegatedSuffix) {
    return function () {
      assertCanWorkWith(this);

      var alwaysSinonMethod =
        'always' + sinonName[0].toUpperCase() + sinonName.substring(1);
      var shouldBeAlways =
        utils.flag(this, 'always') &&
        typeof this._obj[alwaysSinonMethod] === 'function';
      var sinonMethodName = shouldBeAlways ? alwaysSinonMethod : sinonName;

      var messages = getMessages(
        this._obj,
        action,
        nonNegatedSuffix,
        shouldBeAlways,
        slice.call(arguments)
      );
      this.assert(
        this._obj[sinonMethodName].apply(this._obj, arguments),
        messages.affirmative,
        messages.negative
      );
    };
  }

  function sinonMethodAsProperty(name, action, nonNegatedSuffix) {
    var handler = createSinonMethodHandler(name, action, nonNegatedSuffix);
    utils.addProperty(chai.Assertion.prototype, name, handler);
  }

  function exceptionalSinonMethod(
    chaiName,
    sinonName,
    action,
    nonNegatedSuffix
  ) {
    var handler = createSinonMethodHandler(sinonName, action, nonNegatedSuffix);
    utils.addMethod(chai.Assertion.prototype, chaiName, handler);
  }

  function sinonMethod(name, action, nonNegatedSuffix) {
    exceptionalSinonMethod(name, name, action, nonNegatedSuffix);
  }

  utils.addProperty(chai.Assertion.prototype, 'always', function () {
    utils.flag(this, 'always', true);
  });

  sinonProperty(
    'called',
    'been called',
    ' at least once, but it was never called'
  );
  sinonPropertyAsBooleanMethod(
    'callCount',
    'been called exactly %1',
    ', but it was called %c%C'
  );
  sinonProperty(
    'calledOnce',
    'been called exactly once',
    ', but it was called %c%C'
  );
  sinonProperty(
    'calledTwice',
    'been called exactly twice',
    ', but it was called %c%C'
  );
  sinonProperty(
    'calledThrice',
    'been called exactly thrice',
    ', but it was called %c%C'
  );
  sinonMethodAsProperty('calledWithNew', 'been called with new');
  sinonMethod('calledBefore', 'been called before %1');
  sinonMethod('calledAfter', 'been called after %1');
  sinonMethod('calledImmediatelyBefore', 'been called immediately before %1');
  sinonMethod('calledImmediatelyAfter', 'been called immediately after %1');
  sinonMethod(
    'calledOn',
    'been called with %1 as this',
    ', but it was called with %t instead'
  );
  sinonMethod('calledWith', 'been called with arguments %*', '%D');
  sinonMethod(
    'calledOnceWith',
    'been called exactly once with arguments %*',
    '%D'
  );
  sinonMethod('calledWithExactly', 'been called with exact arguments %*', '%D');
  sinonMethod(
    'calledOnceWithExactly',
    'been called exactly once with exact arguments %*',
    '%D'
  );
  sinonMethod(
    'calledWithMatch',
    'been called with arguments matching %*',
    '%D'
  );
  sinonMethod('returned', 'returned %1');
  exceptionalSinonMethod('thrown', 'threw', 'thrown %1');
}