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

Nir Soffer
Fri, 22 Nov 2019 23:42:15 -0000

On Fri, Nov 22, 2019 at 9:55 PM Richard W.M. Jones <rjones@redhat.com>
wrote:
>
> This tests the Python plugin thoroughly by issuing client commands
> through libnbd and checking we get the expected results.
> ---
>  tests/Makefile.am           |  13 +--
>  tests/test-python-plugin.py | 134 ++++++++++++++++++++++++++++
>  tests/test-python.py        | 172 ++++++++++++++++++++++++++++++++++++
>  tests/test.py               |  60 -------------
>  4 files changed, 309 insertions(+), 70 deletions(-)
>
> diff --git a/tests/Makefile.am b/tests/Makefile.am
> index 13cd8f3..88849f5 100644
> --- a/tests/Makefile.am
> +++ b/tests/Makefile.am
> @@ -115,7 +115,8 @@ EXTRA_DIST = \
>         test-pattern-largest-for-qemu.sh \
>         test-python-exception.sh \
>         test.pl \
> -       test.py \
> +       test-python.py \
> +       test-python-plugin.py \
>         test-rate.sh \
>         test-rate-dynamic.sh \
>         test.rb \
> @@ -787,18 +788,10 @@ endif HAVE_PERL
>  if HAVE_PYTHON
>
>  TESTS += \
> +       test-python.py \
>         test-python-exception.sh \
>         test-shebang-python.sh \
>         $(NULL)
> -LIBGUESTFS_TESTS += test-python
> -
> -test_python_SOURCES = test-lang-plugins.c test.h
> -test_python_CFLAGS = \
> -       -DLANG='"python"'
-DSCRIPT='"$(srcdir)/test.py"' \
> -       $(WARNINGS_CFLAGS) \
> -       $(LIBGUESTFS_CFLAGS) \
> -       $(NULL)
> -test_python_LDADD = libtest.la $(LIBGUESTFS_LIBS)
>
>  endif HAVE_PYTHON
>
> diff --git a/tests/test-python-plugin.py b/tests/test-python-plugin.py
> new file mode 100644
> index 0000000..053a380
> --- /dev/null
> +++ b/tests/test-python-plugin.py
> @@ -0,0 +1,134 @@
> +#!/usr/bin/env python3
> +# nbdkit
> +# Copyright (C) 2019 Red Hat Inc.
> +#
> +# Redistribution and use in source and binary forms, with or without
> +# modification, are permitted provided that the following conditions are
> +# met:
> +#
> +# * Redistributions of source code must retain the above copyright
> +# notice, this list of conditions and the following disclaimer.
> +#
> +# * Redistributions in binary form must reproduce the above copyright
> +# notice, this list of conditions and the following disclaimer in the
> +# documentation and/or other materials provided with the distribution.
> +#
> +# * Neither the name of Red Hat nor the names of its contributors may be
> +# used to endorse or promote products derived from this software without
> +# specific prior written permission.
> +#
> +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
> +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
> +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
> +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
> +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
> +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
> +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
> +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
> +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> +# SUCH DAMAGE.
> +
> +# See test-python.py.
> +
> +import nbdkit
> +import sys
> +import pickle
> +import codecs
> +
> +def api_version ():
> +    return 2
> +
> +cfg = {}
> +
> +def config (k, v):
> +    global cfg
> +    if k == "cfg":
> +        cfg = pickle.loads (codecs.decode (v.encode(),
"base64"))
> +
> +def config_complete ():
> +    print ("set_error = %r" % nbdkit.set_error)
> +
> +def open (readonly):
> +    return {
> +        'disk': bytearray (cfg.get ('size', 0))
> +    }
> +
> +def get_size (h):
> +    return len (h['disk'])
> +
> +def is_rotational(h):
> +    return cfg.get ('is_rotational', False)
> +
> +def can_multi_conn (h):
> +    return cfg.get ('can_multi_conn', False)
> +
> +def can_write (h):
> +    return cfg.get ('can_write', True)
> +
> +def can_flush(h):
> +    return cfg.get ('can_flush', False)
> +
> +def can_trim(h):
> +    return cfg.get ('can_trim', False)
> +
> +def can_zero(h):
> +    return cfg.get ('can_zero', False)
> +
> +def can_fast_zero(h):
> +    return cfg.get ('can_fast_zero', False)
> +
> +def can_fua(h):
> +    fua = cfg.get ('can_fua', "none")
> +    if fua == "none":
> +        return nbdkit.FUA_NONE
> +    elif fua == "emulate":
> +        return nbdkit.FUA_EMULATE
> +    elif fua == "native":
> +        return nbdkit.FUA_NATIVE
> +
> +def can_cache(h):
> +    cache = cfg.get ('can_cache', "none")
> +    if cache == "none":
> +        return nbdkit.CACHE_NONE
> +    elif cache == "emulate":
> +        return nbdkit.CACHE_EMULATE
> +    elif cache == "native":
> +        return nbdkit.CACHE_NATIVE
> +
> +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.

> +
> +def pwrite(h, buf, offset, flags):
> +    expect_fua = cfg.get ('pwrite_expect_fua', False)
> +    actual_fua = bool (flags & nbdkit.FLAG_FUA)
> +    assert expect_fua == actual_fua
> +    end = offset + len(buf)
> +    h['disk'][offset:end] = buf
> +
> +def flush(h, flags):
> +    assert flags == 0
> +
> +def trim(h, count, offset, flags):
> +    expect_fua = cfg.get ('trim_expect_fua', False)
> +    actual_fua = bool (flags & nbdkit.FLAG_FUA)
> +    assert expect_fua == actual_fua
> +    h['disk'][offset:offset+count] = bytearray(count)
> +
> +def zero(h, count, offset, flags):
> +    expect_fua = cfg.get ('zero_expect_fua', False)
> +    actual_fua = bool (flags & nbdkit.FLAG_FUA)
> +    assert expect_fua == actual_fua
> +    expect_may_trim = cfg.get ('zero_expect_may_trim', False)
> +    actual_may_trim = bool (flags & nbdkit.FLAG_MAY_TRIM)
> +    assert expect_may_trim == actual_may_trim
> +    expect_fast_zero = cfg.get ('zero_expect_fast_zero', False)
> +    actual_fast_zero = bool (flags & nbdkit.FLAG_FAST_ZERO)
> +    assert expect_fast_zero == actual_fast_zero
> +    h['disk'][offset:offset+count] = bytearray(count)
> +
> +def cache(h, count, offset, flags):
> +    assert flags == 0
> +    # do nothing
> diff --git a/tests/test-python.py b/tests/test-python.py
> new file mode 100755
> index 0000000..2f565ba
> --- /dev/null
> +++ b/tests/test-python.py
> @@ -0,0 +1,172 @@
> +#!/usr/bin/env python3
> +# nbdkit
> +# Copyright (C) 2019 Red Hat Inc.
> +#
> +# Redistribution and use in source and binary forms, with or without
> +# modification, are permitted provided that the following conditions are
> +# met:
> +#
> +# * Redistributions of source code must retain the above copyright
> +# notice, this list of conditions and the following disclaimer.
> +#
> +# * Redistributions in binary form must reproduce the above copyright
> +# notice, this list of conditions and the following disclaimer in the
> +# documentation and/or other materials provided with the distribution.
> +#
> +# * Neither the name of Red Hat nor the names of its contributors may be
> +# used to endorse or promote products derived from this software without
> +# specific prior written permission.
> +#
> +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
> +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
> +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
> +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
> +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
> +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
> +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
> +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
> +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> +# SUCH DAMAGE.
> +
> +# This tests the Python plugin thoroughly by issuing client commands
> +# through libnbd and checking we get the expected results.  It uses an
> +# associated plugin (test-python-plugin.sh).

test-python-plugin.py

This text can use python docstring:

"""
This tests ...
"""

> +
> +import os
> +import sys
> +import pickle
> +import codecs
> +
> +# Python has proven very difficult to valgrind, therefore it is disabled.
> +if "NBDKIT_VALGRIND" in os.environ:
> +    print ("$s: skipping Python test under valgrind" % __file__)
> +    sys.exit (77)
> +
> +try:
> +    import nbd
> +except:

except ImportError:

> +    print ("%s: skipped because cannot import python libnbd" %
__file__)
> +    sys.exit (77)
> +
> +try:
> +    srcdir = os.environ['SRCDIR']
> +except:

except KeyError:

> +    print ("%s: FAIL: test failed because $SRCDIR is not set" %
__file__)
> +    sys.exit (1)
> +
> +def test (cfg):

test will fool testing frameworks, expecting that this is a test function.
Maybe call this handle()? or case()?

> +    h = nbd.NBD ()
> +    cfg = codecs.encode (pickle.dumps (cfg), "base64").decode()

base64.b64encode() is better, avoiding unwanted newlines.

> +    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.

> +
> +# Test the size.
> +h = test ({"size": 512})
> +assert h.get_size() == 512
> +h = test ({"size": 1024*1024})
> +assert h.get_size() == 1024*1024

These tests will fail when on the first error, which is less useful.

With very little work we can convert this to pytest:

def test_size():
   h = test()
   assert h.get_size() == 512

To run the test you use:

pytest test-python.py

> +
> +# Test each flag call.
> +h = test ({"size": 512, "is_rotational": True})
> +assert h.is_rotational()
> +h = test ({"size": 512, "is_rotational": False})
> +assert not h.is_rotational()

When this fails, you will get unhelpful output:

    assert not True

But with pytest you get much more useful error, something like:

    def test_is_rotational():
        h = handle ({"size": 512, "is_rotational":
True})
>       assert not h.is_rotational
E       assert not True
E        +  where True = <test.handle.<locals>.H object at
0x7faa3358e450>.is_rotational

(I faked the handle object for this example)

> +
> +h = test ({"size": 512, "can_multi_conn": True})
> +assert h.can_multi_conn()
> +h = test ({"size": 512, "can_multi_conn": False})
> +assert not h.can_multi_conn()
> +
> +h = test ({"size": 512, "can_write": True})
> +assert not h.is_read_only()
> +h = test ({"size": 512, "can_write": False})
> +assert h.is_read_only()
> +
> +h = test ({"size": 512, "can_flush": True})
> +assert h.can_flush()
> +h = test ({"size": 512, "can_flush": False})
> +assert not h.can_flush()
> +
> +h = test ({"size": 512, "can_trim": True})
> +assert h.can_trim()
> +h = test ({"size": 512, "can_trim": False})
> +assert not h.can_trim()
> +
> +# nbdkit can always zero because it emulates it.
> +#h = test ({"size": 512, "can_zero": True})
> +#assert h.can_zero()
> +#h = test ({"size": 512, "can_zero": False})
> +#assert not h.can_zero()
> +
> +h = test ({"size": 512, "can_fast_zero": True})
> +assert h.can_fast_zero()
> +h = test ({"size": 512, "can_fast_zero": False})
> +assert not h.can_fast_zero()
> +
> +h = test ({"size": 512, "can_fua": "none"})
> +assert not h.can_fua()
> +h = test ({"size": 512, "can_fua":
"emulate"})
> +assert h.can_fua()
> +h = test ({"size": 512, "can_fua":
"native"})
> +assert h.can_fua()
> +
> +h = test ({"size": 512, "can_cache":
"none"})
> +assert not h.can_cache()
> +h = test ({"size": 512, "can_cache":
"emulate"})
> +assert h.can_cache()
> +h = test ({"size": 512, "can_cache":
"native"})
> +assert h.can_cache()
> +
> +# Not yet implemented: can_extents.
> +
> +# Test pread.
> +h = test ({"size": 512})
> +buf = h.pread (512, 0)
> +
> +# Test pwrite + flags.
> +h = test ({"size": 512})
> +h.pwrite (buf, 0)
> +
> +h = test ({"size": 512, "can_fua": "native",
"pwrite_expect_fua": True})
> +h.pwrite (buf, 0, nbd.CMD_FLAG_FUA)
> +
> +# Test flush.
> +h = test ({"size": 512, "can_flush": True})
> +h.flush ()
> +
> +# Test trim + flags.
> +h = test ({"size": 512, "can_trim": True})
> +h.trim (512, 0)
> +
> +h = test ({"size": 512,
> +           "can_trim": True, "can_fua":
"native", "trim_expect_fua": True})

This becomes messy. With the dict does not fit in one line, or
contains more than
few keys it is more readable to use one key: value pair per line.

> +h.trim (512, 0, nbd.CMD_FLAG_FUA)
> +
> +# Test zero + flags.
> +h = test ({"size": 512, "can_zero": True})
> +h.zero (512, 0, nbd.CMD_FLAG_NO_HOLE)
> +
> +h = test ({"size": 512,
> +           "can_zero": True, "can_fua":
"native", "zero_expect_fua": True})
> +h.zero (512, 0, nbd.CMD_FLAG_NO_HOLE | nbd.CMD_FLAG_FUA)
> +
> +h = test ({"size": 512, "can_zero": True,
"zero_expect_may_trim": True})
> +h.zero (512, 0, 0) # absence of nbd.CMD_FLAG_NO_HOLE
> +
> +h = test ({"size": 512,
> +           "can_zero": True, "can_fast_zero": True,
> +           "zero_expect_fast_zero": True})
> +h.zero (512, 0, nbd.CMD_FLAG_NO_HOLE | nbd.CMD_FLAG_FAST_ZERO)
> +
> +# Test cache.
> +h = test ({"size": 512, "can_cache":
"native"})
> +h.cache (512, 0)
> diff --git a/tests/test.py b/tests/test.py
> deleted file mode 100644
> index ac80d96..0000000
> --- a/tests/test.py
> +++ /dev/null
> @@ -1,60 +0,0 @@
> -import nbdkit
> -
> -disk = bytearray(1024*1024)
> -
> -
> -def api_version():
> -    return 2
> -
> -
> -def config_complete():
> -    print ("set_error = %r" % nbdkit.set_error)
> -
> -
> -def open(readonly):
> -    return 1
> -
> -
> -def get_size(h):
> -    global disk
> -    return len(disk)
> -
> -
> -def can_write(h):
> -    return True
> -
> -
> -def can_flush(h):
> -    return True
> -
> -
> -def is_rotational(h):
> -    return False
> -
> -
> -def can_trim(h):
> -    return True
> -
> -
> -def pread(h, count, offset, flags):
> -    global disk
> -    return disk[offset:offset+count]
> -
> -
> -def pwrite(h, buf, offset, flags):
> -    global disk
> -    end = offset + len(buf)
> -    disk[offset:end] = buf
> -
> -
> -def flush(h, flags):
> -    pass
> -
> -
> -def trim(h, count, offset, flags):
> -    pass
> -
> -
> -def zero(h, count, offset, flags):
> -    global disk
> -    disk[offset:offset+count] = bytearray(count)
> --
> 2.23.0
>

Otherwise very nice tests!

Nir