This is a very simple test using https://hypothesis.readthedocs.io to assert that cycling write/read/write/read is lossless for plyfile.PlyData instances. Comment serialization is currently lossy (for eg. ascii whitespace) or throws exceptions (unicode encode errors when not ascii).

plyfile-test.py

import string

from hypothesis import given, strategies as st
from hypothesis.extra.numpy import arrays

#import os, sys; sys.path.insert(0, os.path.abspath('.')); del sys; del os
import plyfile

# Simple strategy for a list of unicode strings
st_comments = st.lists(elements=st.text())
# A useful subset of all valid identifiers (no numbers as they may not lead)
st_valid_names = st.text(min_size=1, alphabet=string.ascii_letters + '_')


@st.composite
def st_structured_arrays(draw, min_size=1, max_size=20):
    """Create arrays that can be described as a valid PlyElement"""
    st_dtypes = st.lists(elements=st.tuples(
        st_valid_names, st.sampled_from(set(plyfile._data_type_reverse))),
                         min_size=1, unique_by=lambda d: d[0])
    return draw(arrays(
        draw(st_dtypes),
        draw(st.integers(min_value=min_size, max_value=max_size)),
        elements=st.binary()))


# Strategy to generate PlyElement instances.  Note that this does not include
# list elements or other more complex datatypes.
st_PlyElement = st.builds(
    target=plyfile.PlyElement.describe,
    data=st_structured_arrays(),
    name=st_valid_names,
    comments=st_comments
    )


# Strategy to generate arbitary PlyData instances
st_PlyData = st.builds(
    target=plyfile.PlyData,
    elements=st.lists(elements=st_PlyElement, unique_by=lambda e: e.name),
    text=st.booleans(),
    byte_order=st.sampled_from(plyfile._byte_order_map.values()),
    comments=st_comments,
    obj_info=st_comments
    )


@given(st_PlyData)
def test_write_read_write(plydata):
    first, second = open('test1.tmp', 'w+b'), open('test2.tmp', 'w+b')
    plydata.write(first)
    first.seek(0)
    plyfile.PlyData.read(first).write(second)
    first.seek(0); second.seek(0)
    assert first.read() == second.read()
    first.close(); second.close()