TST: Use top_level_dir in test discovery.

top_level_dir affects the test case `id` which is used by codecov
to match the source files.

Author: pavoljuhas

Diff for: pyobjcryst/tests/__init__.py

@@ -34,15 +34,17 @@ def testsuite(pattern=''):
         The TestSuite object containing the matching tests.
     '''
     import re
+    from os.path import dirname
     from itertools import chain
     from pkg_resources import resource_filename
     loader = unittest.defaultTestLoader
     thisdir = resource_filename(__name__, '')
-    suite_all = loader.discover(thisdir)
-    # shortcut when pattern is not specified
-    if not pattern:
-        return suite_all
-    # here we need to filter the suite by pattern
+    depth = __name__.count('.') + 1
+    topdir = thisdir
+    for i in range(depth):
+        topdir = dirname(topdir)
+    suite_all = loader.discover(thisdir, top_level_dir=topdir)
+    # always filter the suite by pattern to test-cover the selection code.
     suite = unittest.TestSuite()
     rx = re.compile(pattern)
     tcases = chain.from_iterable(chain.from_iterable(suite_all))
@@ -51,6 +53,8 @@ def testsuite(pattern=''):
         shortname = '.'.join(tcwords[-2:])
         if rx.search(shortname):
             suite.addTest(tc)
+    # verify all tests are found for an empty pattern.
+    assert pattern or suite_all.countTestCases() == suite.countTestCases()
     return suite