svoid test_FactStore() {
  PhilosophyBot1 bot = new([[
    $x weighs $y
      => proc {
        delete all (last time $x weighed $z)
        store      (last time $x weighed $y)
      }
  ]]);
  //bot.printNonMatches = true;
  bot.parseProgram();
  new SimpleFactStore fs;
  fs.verbose = true;
  philosophyBot1_factStore(bot, fs, debug := true);
  bot.addFact("a weighs (50 pounds)");
  bot.addFact("b weighs (55 pounds)");
  bot.think();
  assertEqualsVerbose(ll(
    "last time a weighed (50 pounds)",
    "last time b weighed (55 pounds)"), sorted(fs.facts()));
  bot.addFact("a weighs (52 pounds)");
  bot.think();
  assertEqualsVerbose(ll(
    "last time a weighed (52 pounds)",
    "last time b weighed (55 pounds)"), sorted(fs.facts()));
}