@cucumber/json-to-messages generates TestStepResult#messages as string[] for Behave

[aslakhellesoy]

Summary

A Cucumber Reports user used @cucumber/json-to-messages to convert Behave JSON to messages. One of the messages looks like this (sensitive details edited):

{
  "testStepFinished": {
    "testCaseStartedId": "522e2d20-37f0-4296-87fe-b87069afccec",
    "testStepId": "9c3b9582-d6d2-4f55-88e7-a6d563c57df3",
    "testStepResult": {
      "willBeRetried": false,
      "duration": {
        "seconds": 0,
        "nanos": 0
      },
      "status": "FAILED",
      "message": [
        "Assertion Failed: The pattern isn't contained!!!",
        "Captured stdout:",
        "",
        "",
        "login:",
        " admin",
        "Password:",
        " ",
        "                    Bla bla bla bla                   ",
        "",
        "--------------------------------------------------------------------------------",
        "",
        "Bla bla bla",
        " bla bla"
      ]
    },
    "timestamp": {
      "seconds": 1623180174,
      "nanos": 354000000
    }
  }
}

Expected Behavior

The message field should be a string (with newlines)

Current Behavior

The message field is a string array

Possible Solution

Analyse the output from Behave and determine if the JSON output contains string arrays. If it does, join the string array with \n before setting the message field.

We should also perform JSON schema validation of the generated messages in the same way as we now do for the CCK.
See

common/compatibility-kit/javascript/Makefile

Lines 20 to 22 in 9bf5f76

	acceptance/%.ndjson.valid: features/%.ndjson
	mkdir -p $(@D)
	cat $< | ../../node_modules/.bin/ts-node src/validate.ts > $@