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

tools/test-js-with-puppeteer

@@ -61,40 +61,46 @@ parser.add_argument(
 options = parser.parse_args()
 
 
+def run_single_test(test_file: str, test_number: int, total_tests: int) -> int:
+    cmd = [
+        "node",
+        "--unhandled-rejections=strict",
+        os.path.join(ZULIP_PATH, "node_modules/.bin/ts-node"),
+        "--script-mode",
+        "--transpile-only",
+        test_file,
+    ]
+
+    test_name = os.path.basename(test_file)
+    cmd_str = " ".join(map(shlex.quote, cmd))
+    print(
+        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
+
+    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]:
-        ret = 1
         current_test_num = test_number
         for test_file in test_files[test_number:]:
-            test_name = os.path.basename(test_file)
-            cmd = [
-                "node",
-                "--unhandled-rejections=strict",
-                os.path.join(ZULIP_PATH, "node_modules/.bin/ts-node"),
-                "--script-mode",
-                "--transpile-only",
-                test_file,
-            ]
-            print(
-                "\n\n===================== ({}/{}) {}\nRunning {}\n\n".format(
-                    current_test_num + 1, total_tests, test_name, " ".join(map(shlex.quote, cmd))
-                ),
-                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_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