protected override Task <RunSummary> RunTestCollectionAsync(IMessageBus messageBus, ITestCollection testCollection, IEnumerable <IXunitTestCase> testCases, CancellationTokenSource cancellationTokenSource) => new TestCollectionRunner(testCollection, testCases, DiagnosticMessageSink, messageBus, TestCaseOrderer, new ExceptionAggregator(Aggregator), cancellationTokenSource, _assemblyFixtureMappings, _testNotificationType, ExecutionOptions.MaxParallelThreadsOrDefault()).RunAsync();
