anchor.diff:  
       for (int i = 0; i < levels.length; i++) {
         for (int j = i + 1; j < levels.length; j++) {
  -        expect(levels[i] < levels[j]);
  +        expect(levels[i] < levels[j], isTrue);
         }
       }
     });
  
positive.code: main() {
    test('level comparison is a valid comparator', () {
      var level1 = const Level('NOT_REAL1', 253);
      expect(level1 == level1);
      expect(level1 <= level1);
      expect(level1 >= level1);
      expect(level1 < level1, isFalse);
      expect(level1 > level1, isFalse);
  
      var level2 = const Level('NOT_REAL2', 455);
      expect(level1 <= level2);
      expect(level1 < level2);
      expect(level2 >= level1);
      expect(level2 > level1);
  
      var level3 = const Level('NOT_REAL3', 253);
      expect(level1 !== level3); // different instances
      expect(level1 == level3); // same value.
    });
  
    test('default levels are in order', () {
  
negative.code:       c.level = Level.ALL;
        e.level = Level.OFF;
  
        expect(root.isLoggable(Level.SHOUT), isTrue);
        expect(root.isLoggable(Level.SEVERE), isTrue);
        expect(root.isLoggable(Level.WARNING), isFalse);
        expect(c.isLoggable(Level.FINEST), isTrue);
        expect(c.isLoggable(Level.FINE), isTrue);
        expect(!e.isLoggable(Level.SHOUT), isTrue);
      });
  
      test('add/remove handlers - no hierarchy', () {
  