Add a __main__ for running the test suite.

tests/__main__.py

@@ -0,0 +1,30 @@
+
+import os
+import os.path
+from unittest.main import main
+import sys
+
+
+TEST_ROOT = os.path.dirname(__file__)
+PROJECT_ROOT = os.path.dirname(TEST_ROOT)
+
+executable = 'python3 -m unittest'
+
+if all(arg.startswith('-') for arg in sys.argv[1:]):
+    argv = [executable,
+            'discover',
+            '--start-directory', PROJECT_ROOT,
+            '--top-level-directory', PROJECT_ROOT,
+            ] + sys.argv[1:]
+else:
+    argv = [executable] + sys.argv[1:]
+    for i, arg in enumerate(argv[1:], 1):
+        if arg.startswith('-'):
+            continue
+        mod, _, test = arg.partition(':')
+        mod = mod.rstrip(os.sep)
+        mod = mod.rstrip('.py')
+        mod = mod.replace(os.sep, '.')
+        argv[i] = mod if not test else mod + '.' + test
+
+main(module=None, argv=argv)