Where do crash files and generated tests go in EK9?

  ek9 -fuzztest source.ek9 output.ek9

  ek9 -fuzzmutate source.ek9 mutations/

  manifest.txt: lists each variant with mutation category and location.
  variant_001.ek9, variant_002.ek9, ...: individual mutated files.

  -overwrite     Allow replacing existing output file or directory.
  -seed <n>      Reproducible generation (same seed produces same output).
  -n <n>         Maximum number of candidates (-fuzztest default 200, -fuzzmutate default 100).

  ek9 -fuzztest source.ek9 generated-tests.ek9 -overwrite
  ek9 -fuzzmutate source.ek9 mutations/ -overwrite -test tests.ek9

defines module qa.fuzzingandmutation.crashfiles

  <?-
    Demonstrates code patterns that might produce crash
    files when fuzzed, and test output when generated.
    The output management options ensure CI repeatability.
  -?>

  defines class

    Stack
      items as List of String: List() of String

      push()
        -> item as String
        this.items += item

      pop()
        <- popped as String: String()

        count <- length this.items
        zero <- 0
        emptyDefault <- String()
        if count > zero
          lastIndex <- count - 1
          topItem <- this.items.getOrDefault(lastIndex, emptyDefault)
          if topItem?
            popped: topItem
            this.items -= topItem

      peek() as pure
        <- topItem as String: String()

        count <- length this.items
        zero <- 0
        emptyDefault <- String()
        if count > zero
          lastIndex <- count - 1
          topItem :=? this.items.getOrDefault(lastIndex, emptyDefault)

      size() as pure
        <- count as Integer: length this.items

      operator $ as pure
        <- rtn as String: $this.items

      default operator ?

  defines program

    CrashFilesDemo()
      stdout <- Stdout()

      stack <- Stack()
      stack.push("first")
      stack.push("second")
      stack.push("third")
      stdout.println(`Stack: ${stack}`)

      popped <- stack.pop()
      stdout.println(`Popped: ${popped}`)
      stdout.println(`Peek: ${stack.peek()}`)
      stdout.println(`Size: ${stack.size()}`)