unittest: make unittest.main() work

Enables standalone test scripts to use the common idiom
  if __name__ == '__main__':
      unittest.main()
e.g. https://docs.python.org/3.4/library/unittest.html#basic-example

unittest/metadata.txt

@@ -1,4 +1,4 @@
 srctype = micropython-lib
 type = module
-version = 0.0.7
+version = 0.0.8
 author = Paul Sokolovsky

unittest/test_unittest.py

@@ -0,0 +1,20 @@
+import unittest
+
+class TestStringMethods(unittest.TestCase):
+
+  def test_upper(self):
+      self.assertEqual('foo'.upper(), 'FOO')
+
+  def test_isupper(self):
+      self.assertTrue('FOO'.isupper())
+      self.assertFalse('Foo'.isupper())
+
+  def test_split(self):
+      s = 'hello world'
+      self.assertEqual(s.split(), ['hello', 'world'])
+      # check that s.split fails when the separator is not a string
+      with self.assertRaises(TypeError):
+          s.split(2)
+
+if __name__ == '__main__':
+    unittest.main()

unittest/unittest.py

@@ -116,8 +116,19 @@ def run_class(c, test_result):
 
 
 def main(module="__main__"):
+    def test_cases(m):
+        for tn in dir(m):
+            c = getattr(m, tn)
+            if isinstance(c, object) and isinstance(c, type) and issubclass(c, TestCase):
+                yield c
+
     m = __import__(module)
-    for tn in dir(m):
-        c = getattr(m, tn)
-        if isinstance(c, object) and issubclass(c, TestCase):
-            run_class(c)
+    suite = TestSuite()
+    for c in test_cases(m):
+        suite.addTest(c)
+    runner = TestRunner()
+    result = runner.run(suite)
+    msg = "Ran %d tests" % result.testsRun
+    if result.skippedNum > 0:
+        msg += " (%d skipped)" % result.skippedNum
+    print(msg)