function()

in packages/expect/src/spyMatchers.ts [789:872]
71 lines of code
12 McCabe index (conditional complexity)

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

    const receivedName = received.getMockName();

    const {calls, results} = received.mock;
    const iLast = results.length - 1;

    const pass = iLast >= 0 && isEqualReturn(expected, results[iLast]);

    const message = pass
      ? () => {
          const indexedResults: Array<IndexedResult> = [];
          if (iLast > 0) {
            // Display preceding result as context.
            indexedResults.push([iLast - 1, results[iLast - 1]]);
          }
          indexedResults.push([iLast, results[iLast]]);

          return (
            // eslint-disable-next-line prefer-template
            matcherHint(matcherName, receivedName, expectedArgument, options) +
            '\n\n' +
            `Expected: not ${printExpected(expected)}\n` +
            (results.length === 1 &&
            results[0].type === 'return' &&
            stringify(results[0].value) === stringify(expected)
              ? ''
              : printReceivedResults(
                  'Received:     ',
                  expected,
                  indexedResults,
                  results.length === 1,
                  iLast,
                )) +
            printNumberOfReturns(countReturns(results), calls.length)
          );
        }
      : () => {
          const indexedResults: Array<IndexedResult> = [];
          if (iLast >= 0) {
            if (iLast > 0) {
              let i = iLast - 1;
              // Is there a preceding result that is equal to expected value?
              while (i >= 0 && !isEqualReturn(expected, results[i])) {
                i -= 1;
              }
              if (i < 0) {
                i = iLast - 1; // otherwise, preceding result
              }

              indexedResults.push([i, results[i]]);
            }

            indexedResults.push([iLast, results[iLast]]);
          }

          return (
            // eslint-disable-next-line prefer-template
            matcherHint(matcherName, receivedName, expectedArgument, options) +
            '\n\n' +
            `Expected: ${printExpected(expected)}\n` +
            printReceivedResults(
              'Received: ',
              expected,
              indexedResults,
              results.length === 1,
              iLast,
            ) +
            printNumberOfReturns(countReturns(results), calls.length)
          );
        };

    return {message, pass};
  };