refactor: Extract code of running a single puppeteer test into a function.

tools/test-js-with-puppeteer

@@ -61,16 +61,7 @@ parser.add_argument(
 options = parser.parse_args()
 
 
-def run_tests(files: Iterable[str], external_host: str) -> None:
-    test_dir = os.path.join(ZULIP_PATH, "frontend_tests/puppeteer_tests")
-    test_files = find_js_test_files(test_dir, files)
-    total_tests = len(test_files)
-
-    def run_tests(test_number: int = 0) -> Tuple[int, int]:
-        ret = 1
-        current_test_num = test_number
-        for test_file in test_files[test_number:]:
-            test_name = os.path.basename(test_file)
+def run_single_test(test_file: str, test_number: int, total_tests: int) -> int:
     cmd = [
         "node",
         "--unhandled-rejections=strict",
@@ -79,22 +70,37 @@ def run_tests(files: Iterable[str], external_host: str) -> None:
         "--transpile-only",
         test_file,
     ]
+
+    test_name = os.path.basename(test_file)
+    cmd_str = " ".join(map(shlex.quote, cmd))
     print(
-                "\n\n===================== ({}/{}) {}\nRunning {}\n\n".format(
-                    current_test_num + 1, total_tests, test_name, " ".join(map(shlex.quote, cmd))
-                ),
+        f"\n\n===================== ({test_number}/{total_tests}) {test_name} =====================\nRunning {cmd_str}\n\n",
         flush=True,
     )
+
     ret = subprocess.call(cmd)
 
     # Resetting test environment.
     reset_zulip_test_database()
+
     # We are calling to /flush_caches to remove all the server-side caches.
     response = requests.post("http://zulip.zulipdev.com:9981/flush_caches")
     assert response.status_code == 200
 
-            if ret != 0:
-                return ret, current_test_num
+    return ret
+
+
+def run_tests(files: Iterable[str], external_host: str) -> None:
+    test_dir = os.path.join(ZULIP_PATH, "frontend_tests/puppeteer_tests")
+    test_files = find_js_test_files(test_dir, files)
+    total_tests = len(test_files)
+
+    def run_tests(test_number: int = 0) -> Tuple[int, int]:
+        current_test_num = test_number
+        for test_file in test_files[test_number:]:
+            return_code = run_single_test(test_file, current_test_num + 1, total_tests)
+            if return_code != 0:
+                return return_code, current_test_num
             current_test_num += 1
         return 0, -1