[Libguestfs] [PATCH nbdkit v2 10/10] tests: Test the Python plugin thoroughly.

[Richard W.M. Jones]

On Sat, Nov 23, 2019 at 01:42:15AM +0200, Nir Soffer wrote:
> On Fri, Nov 22, 2019 at 9:55 PM Richard W.M. Jones <rjones at redhat.com> wrote:
> > +def pread(h, count, offset, flags):
> > +    assert flags == 0
> > +    return h['disk'][offset:offset+count]
> 
> Very nice and simple test plugin!
> 
> But this returns always a bytearray, which is also what nbdkit python plugin
> expects. But real code using HTTPConnection return bytes:
> 
> >>> c = http.client.HTTPSConnection("www.python.org")
> >>> c.request("GET", "/")
> >>> r = c.getresponse()
> >>> r.read()[:10]
> b'<!doctype '
> 
> I think the plugin should support both bytearray, memoryview, or
> bytes. Supporting objects
> implementing the buffer protocol would be best.

I thought bytearray & bytes were the same thing :-/

Would adding this break existing nbdkit Python scripts?  Should this
be considered for v2 of the API?  Are there performance implications /
improvements from doing this?

> test-python-plugin.py
> 
> This text can use python docstring:
> 
> """
> This tests ...
> """

Good point, I'll fix this.  We could probably also have nbdkit do
something with the docstring, such as printing it in --help output,
although that's something for another patch series.

> > +    h = nbd.NBD ()
> > +    cfg = codecs.encode (pickle.dumps (cfg), "base64").decode()
> 
> base64.b64encode() is better, avoiding unwanted newlines.

Ah OK, I originally added strip(), but this is better.

> > +    cmd = ["nbdkit", "-v", "-s", "--exit-with-parent",
> > +           "python", srcdir + "/test-python-plugin.py",
> > +           "cfg=" + cfg]
> > +    h.connect_command (cmd)
> > +    return h
> > +
> > +# Test we can send an empty pickled test configuration and do nothing
> > +# else.  This is just to ensure the machinery of the test works.
> > +h = test ({})
> 
> So we have now running nbdkit that will exit the python collects when h
> is implicitly closed when creating a new handle?
> 
> This is fragile, but can be solved with the help of a testing framework.
[...]
> pytest test-python.py

I'll probably use unittest though because it's built into Python and
because it's what we use in libguestfs, hivex etc but yes good idea.

Thanks,

Rich.

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