private val writeFaults: MutableSet<Path> = LinkedHashSet()
  private val deleteFaults: MutableSet<Path> = LinkedHashSet()
  private val renameFaults: MutableSet<Path> = LinkedHashSet()

  fun setFaultyWrite(
    file: Path,
    faulty: Boolean,
  ) {
    if (faulty) {
      writeFaults.add(file)
    } else {
      writeFaults.remove(file)
    }
  }

  fun setFaultyDelete(
    file: Path,

    set("a", "a", "a")
    set("b", "b", "b")

    // We can't begin the edit if writing 'DIRTY' fails.
    filesystem.setFaultyWrite(journalFile, true)
    assertThat(cache.edit("c")).isNull()

    // Once the journal has a failure, subsequent writes aren't permitted.
    filesystem.setFaultyWrite(journalFile, false)
    assertThat(cache.edit("d")).isNull()