Firehose putRecordBatch not working

[YTvW]

I try to use this library and jest to unit test a lambda function.

But the mock does not seem to do its job, the sdk call goes to the actual service instead of using the mocked function.
The Firehose client get initiated inside of the handler.

      const response = {
        FailedPutCount: 0,
        RequestResponses: map(params.Records, (record) => {
          return { RecordId: "test" };
        }),
      };
      callback(null, response);
    });```