fix(iperf): fix incorrect test expectation logic

examples/ethernet/iperf/pytest_eth_iperf.py

@@ -30,6 +30,12 @@ except ImportError:
 NO_BANDWIDTH_LIMIT = -1  # iperf send bandwidth is not limited
 
 
+def get_ip_and_wait_prompt(dut: Dut) -> Any:
+    dut_ip = dut.expect(r'esp_netif_handlers: .+ ip: (\d+\.\d+\.\d+\.\d+),').group(1)
+    dut.expect('iperf>')
+    return dut_ip
+
+
 class IperfTestUtilityEth(IperfUtility.IperfTestUtility):
     """iperf test implementation"""
 
@@ -52,9 +58,7 @@ class IperfTestUtilityEth(IperfUtility.IperfTestUtility):
         except subprocess.CalledProcessError:
             pass
         self.dut.write('restart')
-        self.dut.expect("Type 'help' to get the list of commands.")
-        self.dut.expect('iperf>')
-        dut_ip = self.dut.expect(r'esp_netif_handlers: .+ ip: (\d+\.\d+\.\d+\.\d+),').group(1)
+        dut_ip = get_ip_and_wait_prompt(self.dut)
         rssi = 0
         return dut_ip, rssi
 
@@ -73,12 +77,11 @@ def test_esp_eth_iperf(
       2. compare with the pre-defined pass standard
     """
 
-    # 1. wait for DUT
-    dut.expect_exact('iperf>')
+    # 1. wait for DUT to be ready
+    dut_ip = get_ip_and_wait_prompt(dut)
 
     # 2. preparing
     pc_iperf_log_file = os.path.join(dut.logdir, 'pc_iperf_log.md')
-    dut_ip = dut.expect(r'esp_netif_handlers: .+ ip: (\d+\.\d+\.\d+\.\d+),').group(1)
     pc_nic_ip = get_host_ip4_by_dest_ip(dut_ip)
     test_result = {
         'tcp_tx': IperfUtility.TestResult('tcp', 'tx', 'ethernet'),