function()

in packages/expect/src/spyMatchers.ts [704:786]
70 lines of code
13 McCabe index (conditional complexity)

  function (
    this: MatcherState,
    received: any,
    ...expected: Array<unknown>
  ): SyncExpectationResult {
    const expectedArgument = '...expected';
    const options: MatcherHintOptions = {
      isNot: this.isNot,
      promise: this.promise,
    };
    ensureMockOrSpy(received, matcherName, expectedArgument, options);

    const receivedIsSpy = isSpy(received);
    const receivedName = receivedIsSpy ? 'spy' : received.getMockName();

    const calls = receivedIsSpy
      ? received.calls.all().map((x: any) => x.args)
      : received.mock.calls;
    const iLast = calls.length - 1;

    const pass = iLast >= 0 && isEqualCall(expected, calls[iLast]);

    const message = pass
      ? () => {
          const indexedCalls: Array<IndexedCall> = [];
          if (iLast > 0) {
            // Display preceding call as context.
            indexedCalls.push([iLast - 1, calls[iLast - 1]]);
          }
          indexedCalls.push([iLast, calls[iLast]]);

          return (
            // eslint-disable-next-line prefer-template
            matcherHint(matcherName, receivedName, expectedArgument, options) +
            '\n\n' +
            `Expected: not ${printExpectedArgs(expected)}\n` +
            (calls.length === 1 && stringify(calls[0]) === stringify(expected)
              ? ''
              : printReceivedCallsNegative(
                  expected,
                  indexedCalls,
                  calls.length === 1,
                  iLast,
                )) +
            `\nNumber of calls: ${printReceived(calls.length)}`
          );
        }
      : () => {
          const indexedCalls: Array<IndexedCall> = [];
          if (iLast >= 0) {
            if (iLast > 0) {
              let i = iLast - 1;
              // Is there a preceding call that is equal to expected args?
              while (i >= 0 && !isEqualCall(expected, calls[i])) {
                i -= 1;
              }
              if (i < 0) {
                i = iLast - 1; // otherwise, preceding call
              }

              indexedCalls.push([i, calls[i]]);
            }

            indexedCalls.push([iLast, calls[iLast]]);
          }

          return (
            // eslint-disable-next-line prefer-template
            matcherHint(matcherName, receivedName, expectedArgument, options) +
            '\n\n' +
            printExpectedReceivedCallsPositive(
              expected,
              indexedCalls,
              isExpand(this.expand),
              calls.length === 1,
              iLast,
            ) +
            `\nNumber of calls: ${printReceived(calls.length)}`
          );
        };

    return {message, pass};
  };