How to unit test multiple events (type: reduce)

[yvespp]

I want to unit test my reduce config by sending multiple events and then check that I get one combined event out. How can I do that?
I tried with multiple input events but that seems to pass only one event at the time:

transforms:
  kubernetes_transform:
    type: remap
    inputs:
      - kubernetes_logs
      ...
  kubernetes_logs_full:
    type: reduce
    inputs:
      - kubernetes_transform
    ends_when: ".LogEntryType == \"F\""
    ...
  - name: "kube log parsing"
    inputs:
      - insert_at: "kubernetes_transform"
        type: "log"
        log_fields:
          .file: /var/log/containers/influxdb-influxdb-864c4f54cb-7vhct_influxdb_influxdb-influxdb-ed9971dddc34ccafd6f572659aa40cb895d4fa013fe1aa8fc9c805febdbd8a0e.log
          .host: vector-9fxtp
          .message: 2022-02-11T17:39:27.684933558Z stderr P line1
          .source_type: file
      - insert_at: "kubernetes_transform"
        type: "log"
        log_fields:
          .file: /var/log/containers/influxdb-influxdb-864c4f54cb-7vhct_influxdb_influxdb-influxdb-ed9971dddc34ccafd6f572659aa40cb895d4fa013fe1aa8fc9c805febdbd8a0e.log
          .host: vector-9fxtp
          .message: 2022-02-11T17:39:27.684933558Z stderr F line2
          .source_type: file
    outputs:
      - extract_from: "kubernetes_logs_full"
        conditions:
          - type: "vrl"
            source: |
              assert!(is_timestamp(.timestamp))
              assert_eq!(.LogMessage, "line1line2")

I also tried with vrl source to pass an array:

transforms:
  kubernetes_transform:
    type: remap
    inputs:
      - kubernetes_logs
      ...
  kubernetes_logs_full:
    type: reduce
    inputs:
      - kubernetes_transform
    ends_when: ".LogEntryType == \"F\""
    ...
  - name: "kube log parsing"
    inputs:
      - insert_at: "kubernetes_transform"
        type: "vrl"
        source: |
          . = [
            {
              "file": "/var/log/containers/influxdb-influxdb-864c4f54cb-7vhct_influxdb_influxdb-influxdb-ed9971dddc34ccafd6f572659aa40cb895d4fa013fe1aa8fc9c805febdbd8a0e.log",
              "host": "vector-9fxtp",
              "message": "2022-02-11T17:39:27.684933558Z stderr P line1",
              "source_type": "file"
            },
            {
              "file": "/var/log/containers/influxdb-influxdb-864c4f54cb-7vhct_influxdb_influxdb-influxdb-ed9971dddc34ccafd6f572659aa40cb895d4fa013fe1aa8fc9c805febdbd8a0e.log",
              "host": "vector-9fxtp",
              "message": "2022-02-11T17:39:27.684933558Z stderr F line2",
              "source_type": "file"
            }
          ]
    outputs:
      - extract_from: "kubernetes_logs_full"
        conditions:
          - type: "vrl"
            source: |
              assert!(is_timestamp(.timestamp))
              assert_eq!(.LogMessage, "line1line2")

[jszwedko]

Mmm, that looks like a gap in the unit testing framework. I believe it sends, flushes, and tests each output event. I think this would make sense as an enhancement request if you want to open one.