tests: generate AVL vs WAVL difference by contradiction

Signed-off-by: Matej Focko <mfocko@redhat.com>

test_generate.py

@@ -4,6 +4,7 @@ from comparator import Comparator
 from test_wavl import delete_strategy
 
 import hypothesis
+import pytest
 
 
 def report_different(before, deleted, comparator):
@@ -16,9 +17,10 @@ def report_different(before, deleted, comparator):
         print(comparator, file=a)
 
 
+@pytest.mark.xfail
 @hypothesis.settings(max_examples=10000, deadline=None)
 @hypothesis.given(config=delete_strategy())
-def test_delete(config):
+def test_delete_ranks_differ(config):
     values, order = config
 
     comparator = Comparator(AVLTree(), WAVLTree())
@@ -35,3 +37,25 @@ def test_delete(config):
         except AssertionError:
             report_different(before, value, comparator)
             raise
+
+
+@pytest.mark.xfail
+@hypothesis.settings(max_examples=10000, deadline=None)
+@hypothesis.given(config=delete_strategy())
+def test_delete_trees_differ(config):
+    values, order = config
+
+    comparator = Comparator(AVLTree(), WAVLTree())
+
+    for value in values:
+        comparator.insert(value)
+
+    for value in order:
+        before = str(comparator.left)
+        comparator.delete(value)
+
+        try:
+            assert comparator.are_similar
+        except AssertionError:
+            report_different(before, value, comparator)
+            raise