Tests can no longer use db in memory: doesn't work with multiple threads.

IPython/testing/tools.py

@@ -167,7 +167,8 b' def default_config():'
     config.TerminalInteractiveShell.colors = 'NoColor'
     config.TerminalTerminalInteractiveShell.term_title = False,
     config.TerminalInteractiveShell.autocall = 0
-    config.HistoryManager.hist_file = u':memory:'
+    config.HistoryManager.hist_file = u'test_hist.sqlite'
+    config.HistoryManager.db_cache_size = 10000
     return config