add a previously failing test

This was fixed by #268

Author: basnijholt

adaptive/tests/test_sequence_learner.py

@@ -0,0 +1,26 @@
+import asyncio
+
+from adaptive import Runner, SequenceLearner
+from adaptive.runner import SequentialExecutor
+
+
+class FailOnce:
+    def __init__(self):
+        self.failed = False
+
+    def __call__(self, value):
+        if self.failed:
+            return value
+        self.failed = True
+        raise RuntimeError
+
+
+def test_fail_with_sequence_of_unhashable():
+    # https://github.com/python-adaptive/adaptive/issues/265
+    seq = [{1: 1}]  # unhashable
+    learner = SequenceLearner(FailOnce(), sequence=seq)
+    runner = Runner(
+        learner, goal=SequenceLearner.done, retries=1, executor=SequentialExecutor()
+    )
+    asyncio.get_event_loop().run_until_complete(runner.task)
+    assert runner.status() == "finished"