Add testing regressions of pydot vs graphviz

Author: prmtl

test/test_rendering_dot_files.py

@@ -0,0 +1,90 @@
+from __future__ import division
+from __future__ import print_function
+
+import glob
+import os
+import subprocess
+import sys
+from hashlib import sha256
+
+import pydot_ng as pydot
+
+PY3 = not sys.version_info < (3, 0, 0)
+
+if PY3:
+    NULL_SEP = b''
+    xrange = range
+else:
+    NULL_SEP = ''
+    bytes = str
+
+DOT_BINARY_PATH = pydot.find_graphviz()['dot']
+
+
+TEST_DIR = os.path.dirname(__file__)
+REGRESSION_TESTS_DIR = os.path.join(TEST_DIR, "graphs")
+MY_REGRESSION_TESTS_DIR = os.path.join(TEST_DIR, "my_tests")
+
+TESTS_DIRS = (
+    ("regressions", REGRESSION_TESTS_DIR),
+    ("my_regressions", MY_REGRESSION_TESTS_DIR),
+)
+
+
+def list_dots(path):
+    searchpath = os.path.join(path, "*.dot")
+    return [f for f in glob.glob(searchpath)]
+
+
+def pytest_generate_tests(metafunc):
+    idlist = []
+    argvalues = []
+    for name, dir in TESTS_DIRS:
+        for filepath in list_dots(dir):
+            filename = os.path.basename(filepath)
+            idlist.append("{}-{}".format(name, filename))
+            argvalues.append((filepath,))
+    metafunc.parametrize(
+        argnames=["filepath"],
+        argvalues=argvalues,
+        ids=idlist,
+        scope="function",
+    )
+
+
+def test_render_and_compare_dot_files(filepath):
+    def _render_with_graphviz(filename):
+        p = subprocess.Popen(
+            (DOT_BINARY_PATH, '-Tjpe'),
+            cwd=os.path.dirname(filename),
+            stdin=open(filename, 'rt'),
+            stderr=subprocess.PIPE, stdout=subprocess.PIPE)
+
+        stdout = p.stdout
+
+        stdout_output = list()
+        while True:
+            data = stdout.read()
+            if not data:
+                break
+            stdout_output.append(data)
+        stdout.close()
+
+        if stdout_output:
+            stdout_output = NULL_SEP.join(stdout_output)
+
+        # this returns a status code we should check
+        p.wait()
+
+        return sha256(stdout_output).hexdigest()
+
+    def _render_with_pydot(filename):
+        g = pydot.graph_from_dot_file(filename)
+        if not isinstance(g, list):
+            g = [g]
+        jpe_data = NULL_SEP.join([_g.create(format='jpe') for _g in g])
+        return sha256(jpe_data).hexdigest()
+    parsed_data_hexdigest = _render_with_pydot(filepath)
+    original_data_hexdigest = _render_with_graphviz(filepath)
+
+    assert original_data_hexdigest == parsed_data_hexdigest