Split functionality out of main

This commit splits out the actual output generation functionality from
the main function. It also adds parameters for specifying a stdin and
stdout file object. This enables external access to the output
generation within python, which could be useful for integrating
subunit-trace output with your own test runner.

Change-Id: Id9fc13b9b70c5b2cc47b48eee6426e7e312eff7f

os_testr/subunit_trace.py

@@ -344,21 +344,22 @@ def parse_args():
     return parser.parse_args()
 
 
-def main():
-    args = parse_args()
+def trace(stdin, stdout, print_failures=False, failonly=False,
+          enable_diff=False, abbreviate=False, color=False, post_fails=False,
+          no_summary=False):
     stream = subunit.ByteStreamToStreamResult(
-        sys.stdin, non_subunit_name='stdout')
+        stdin, non_subunit_name='stdout')
     outcomes = testtools.StreamToDict(
-        functools.partial(show_outcome, sys.stdout,
-                          print_failures=args.print_failures,
-                          failonly=args.failonly,
-                          enable_diff=args.enable_diff,
-                          abbreviate=args.abbreviate,
-                          enable_color=args.color))
+        functools.partial(show_outcome, stdout,
+                          print_failures=print_failures,
+                          failonly=failonly,
+                          enable_diff=enable_diff,
+                          abbreviate=abbreviate,
+                          enable_color=color))
     summary = testtools.StreamSummary()
     result = testtools.CopyStreamResult([outcomes, summary])
     result = testtools.StreamResultRouter(result)
-    cat = subunit.test_results.CatFiles(sys.stdout)
+    cat = subunit.test_results.CatFiles(stdout)
     result.add_rule(cat, 'test_id', test_id=None)
     start_time = datetime.datetime.utcnow()
     result.startTestRun()
@@ -371,18 +372,25 @@ def main():
 
     if count_tests('status', '.*') == 0:
         print("The test run didn't actually run any tests")
-        exit(1)
-    if args.post_fails:
-        print_fails(sys.stdout)
-    if not args.no_summary:
-        print_summary(sys.stdout, elapsed_time)
+        return 1
+    if post_fails:
+        print_fails(stdout)
+    if not no_summary:
+        print_summary(stdout, elapsed_time)
 
     # NOTE(mtreinish): Ideally this should live in testtools streamSummary
     # this is just in place until the behavior lands there (if it ever does)
     if count_tests('status', '^success$') == 0:
         print("\nNo tests were successful during the run")
-        exit(1)
-    exit(0 if summary.wasSuccessful() else 1)
+        return 1
+    return 0 if summary.wasSuccessful() else 1
+
+
+def main():
+    args = parse_args()
+    exit(trace(sys.stdin, sys.stdout, args.print_failures, args.failonly,
+               args.enable_diff, args.abbreviate, args.color, args.post_fails,
+               args.no_summary))
 
 
 if __name__ == '__main__':

os_testr/tests/test_subunit_trace.py

@@ -14,13 +14,16 @@
 # under the License.
 
 from datetime import datetime as dt
+import io
 import os
 import subprocess
+import sys
 
 from ddt import data
 from ddt import ddt
 from ddt import unpack
 from mock import patch
+import six
 
 from os_testr import subunit_trace
 from os_testr.tests import base
@@ -79,3 +82,15 @@ class TestSubunitTrace(base.TestCase):
         with open(regular_stream, 'rb') as stream:
             p.communicate(stream.read())
         self.assertEqual(0, p.returncode)
+
+    def test_trace(self):
+        regular_stream = os.path.join(
+            os.path.dirname(os.path.abspath(__file__)),
+            'sample_streams/successful.subunit')
+        bytes_ = io.BytesIO()
+        with open(regular_stream, 'rb') as stream:
+            bytes_.write(six.binary_type(stream.read()))
+        bytes_.seek(0)
+        stdin = io.TextIOWrapper(io.BufferedReader(bytes_))
+        returncode = subunit_trace.trace(stdin, sys.stdout)
+        self.assertEqual(0, returncode)