[Xapian-tickets] [Xapian] #337: Extend test of behaviour of databases after close

[Xapian]

#337: Extend test of behaviour of databases after close
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 Reporter:  richard       |             Owner:  gp1308
     Type:  defect        |            Status:  new
 Priority:  low           |         Milestone:  1.4.x
Component:  Test Suite    |           Version:  SVN trunk
 Severity:  normal        |        Resolution:
 Keywords:  GoodFirstBug  |        Blocked By:
 Blocking:                |  Operating System:  All
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Comment (by olly):

 I think you're coming at this the wrong way.

 A testcase is meant to test what the implemented behaviour should be, not
 what how a particular implementation behaves.

 So when as here there's a current implementation, you shouldn't start by
 testing the current implementation and then writing the test based on
 that.  The current implementation could be wrong, and if it is then
 discovering that is a useful result from this exercise (previous added
 test coverage here uncovered a bug - see
 2b40b693c2dd15a196b7f2699ec848f804595f80).

 So instead think about what the behaviour of these methods should be after
 `close()` and write a test for that.

 The documented behaviour is that the method should either behave as it
 would have before `close()` was called or else throw `DatabaseError`.

 For `commit()`, the pre-`close()` behaviour when there are no pending
 changes is actually to do nothing so the local behaviour is OK (though a
 little odd at first sight).  And the remote behaviour is also OK.  But it
 would also be OK for the local behaviour to be throwing an exception
 and/or for the remote behaviour to be doing nothing so the testcase should
 accept either behaviour and not test which happens depending on the
 backend name.  That's also what existing checks in this testcase are
 doing.

 For transactions, the transaction has no observable effect unless anything
 is done within it, so it's probably OK for the calls to do nothing, and
 it's certainly OK to throw `DatabaseError`.

 If `begin_transaction()` fails, you aren't in a transaction, so
 `commit_transaction()` throwing `InvalidOperationError` is correct.  If
 `begin_transaction()` succeeds, then `commit_transaction()` should either
 work or throw `DatabaseError`.

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Ticket URL: <https://trac.xapian.org/ticket/337#comment:14>
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