operation validateTree(tree, label) {
  tree.label = label;
  runTarget("validate-tree");
  return EVL!UnsatisfiedConstraint.all;
}

@test
operation valid() {
  var tree = new Tree!Tree;
  var errors = validateTree(tree, "t1n");
  assertEquals(0, errors.size);
}

@test
operation error() {
  var tree = new Tree!Tree;
  var errors = validateTree(tree, "1n");
  assertEquals(1, errors.size);
  var error = errors.first;
  assertEquals(tree, error.instance);
  assertEquals(false, error.constraint.isCritique);
  assertEquals("LabelsStartWithT", error.constraint.name);
}

@test
operation warning() {
  var tree = new Tree!Tree;
  var errors = validateTree(tree, "t1");
  assertEquals(1, errors.size);
  var error = errors.first;
  assertEquals(tree, error.instance);
  assertEquals(true, error.constraint.isCritique);
  assertEquals("LabelsEndInN", error.constraint.name);
}