Tests: Extend test-lib script to support coverage parameter & add to test-main

tools/test-lib

@@ -1,19 +1,34 @@
 #!/usr/bin/env python
 
-import coverage
 import os
 import sys
 import unittest
+import argparse
 
 from importlib import import_module
 
+def parse_args():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--coverage',
+                        nargs='?',
+                        const=True,
+                        default=False,
+                        help='compute test coverage ("--coverage combine" to combine with previous reports)')
+    return parser.parse_args()
+
 def run_all():
     TOOLS_DIR = os.path.dirname(os.path.abspath(__file__))
     ROOT_DIR = os.path.abspath(os.path.join(TOOLS_DIR, '..'))
     BOTS_DIR = os.path.join(ROOT_DIR, 'zulib_bots')
     sys.path.insert(0, BOTS_DIR)
 
+    options = parse_args()
+
+    if options.coverage:
+        import coverage
         cov = coverage.Coverage(config_file="tools/.coveragerc")
+        if options.coverage == 'combine':
+            cov.load()
         cov.start()
 
     module = import_module('zulip_bots.lib_tests')
@@ -25,6 +40,7 @@ def run_all():
     if result.failures or result.errors:
         sys.exit(1)
 
+    if not result.failures and options.coverage:
         cov.stop()
         cov.data_suffix = False  # Disable suffix so that filename is .coverage
         cov.save()

tools/test-main

@@ -5,3 +5,4 @@ set -ev
 tools/test-bots --coverage
 tools/test-botserver --coverage combine
 tools/test-zulip --coverage combine
+tools/test-lib --coverage combine