test_handler: Support running various tests using pytest.

This enables use of pytest with:
* the zulip package
* the botserver package

tools/server_lib/test_handler.py

@@ -4,6 +4,7 @@ import os
 import sys
 import argparse
 import unittest
+import pytest
 
 TOOLS_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 os.chdir(os.path.dirname(TOOLS_DIR))
@@ -15,6 +16,14 @@ def handle_input_and_run_tests_for_package(package_name):
                         const=True,
                         default=False,
                         help='compute test coverage (--coverage combine to combine with previous reports)')
+    parser.add_argument('--pytest', '-p',
+                        default=False,
+                        action='store_true',
+                        help="run tests with pytest")
+    parser.add_argument('--verbose', '-v',
+                        default=False,
+                        action='store_true',
+                        help='show verbose output (with pytest)')
     options = parser.parse_args()
 
     if options.coverage:
@@ -24,16 +33,32 @@ def handle_input_and_run_tests_for_package(package_name):
             cov.load()
         cov.start()
 
+    if options.pytest:
+        location_to_run_in = os.path.join(TOOLS_DIR, '..', package_name)
+        paths_to_test = ['.']
+        pytest_options = [
+            '-s',    # show output from tests; this hides the progress bar though
+            '-x',    # stop on first test failure
+            '--ff',  # runs last failure first
+        ]
+        pytest_options += (['-v'] if options.verbose else [])
+        os.chdir(location_to_run_in)
+        result = pytest.main(paths_to_test + pytest_options)
+        if result != 0:
+            sys.exit(1)
+        failures = False
+    else:
         # Codecov seems to work only when using loader.discover. It failed to capture line executions
         # for functions like loader.loadTestFromModule or loader.loadTestFromNames.
         test_suites = unittest.defaultTestLoader.discover(package_name)
         suite = unittest.TestSuite(test_suites)
         runner = unittest.TextTestRunner(verbosity=2)
         result = runner.run(suite)
+        failures = result.failures
         if result.failures or result.errors:
             sys.exit(1)
 
-    if not result.failures and options.coverage:
+    if not failures and options.coverage:
         cov.stop()
         cov.data_suffix = False  # Disable suffix so that filename is .coverage
         cov.save()