Testing - Network Layer Fault Injection in Ruby

Hi all,

I’ve yet to find something that fills this hole in my test cases.

Does anyone do this, and if so, what tools do they use?

Thanks,

James.

On Oct 14, 2007, at 13:23 , James T. wrote:

I’ve yet to find something that fills this hole in my test cases.
Does anyone do this, and if so, what tools do they use?

I do some of this with custom stubs in memcache-client, see below.
I’ve also simulated call failures (Errno::whatever) with slightly
more powerful stubs that can take a block to raise the exception.

Here’s a fake socket:

class FakeSocket

attr_reader :written, :data

def initialize
@written = StringIO.new
@data = StringIO.new
end

def write(data)
@written.write data
end

def gets
@data.gets
end

def read(arg)
@data.read arg
end

end

And here’s a test using it:

def test_flush_all_failure
socket = FakeSocket.new
socket.data.write “ERROR\r\n”
socket.data.rewind
server = FakeServer.new socket
def server.host() “localhost”; end
def server.port() 11211; end

 @cache.servers = []
 @cache.servers << server

 assert_raise MemCache::MemCacheError do
   @cache.flush_all
 end

 assert_equal "flush_all\r\n", socket.written.string

end

Eric,

Thanks, that’s somewhat the route I had started down for some of the
units. I probably shouldn’t have omitted from my orignal question, the
fact that I’m also using OpenSSL.

Some of the specific issues I have been dealing with are caused by a
harsh environment (trans-atlantic links and poor ADSL connections), and
in some cases this causes irrecoverable blocking. I think I’ve managed
to cover all of the blocking cases, but local tests are hard to
implement, as you have to fake things like a full TCP connection
timeout. (Which requires not sending and timing out packet data which
normally the OS doesn’t want you to do).

It’s also difficult to find out where the blocks are, as the state
renders the app essentially useless, and happens in a different
environment than that of the testing / development stage.

As some of this connection state stuff is actually outside of pure ruby,
I was somewhat hoping for an external solution, such as a fault
injection proxy socket or similar. Do you know of any?

Regards,

James.

On Oct 14, 2007, at 14:52 , James T. wrote:

packet data which normally the OS doesn’t want you to do).

It’s also difficult to find out where the blocks are, as the state
renders the app essentially useless, and happens in a different
environment than that of the testing / development stage.

As some of this connection state stuff is actually outside of pure
ruby, I was somewhat hoping for an external solution, such as a
fault injection proxy socket or similar. Do you know of any?

I don’t I’ve not needed that level of fault tolerance.

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