Ensure that a serial port is ready before running unit tests on a remote target // Resolve #3742

HISTORY.rst

@@ -27,6 +27,10 @@ PlatformIO Core 5
     * `Cppcheck <https://docs.platformio.org/page/plus/check-tools/cppcheck.html>`__ v2.4.1 with new checks and MISRA improvements
     * `PVS-Studio <https://docs.platformio.org/page/plus/check-tools/pvs-studio.html>`__ v7.12 with new diagnostics and extended capabilities for security and safety standards
 
+* **Miscellaneous**
+
+  - Ensure that a serial port is ready before running unit tests on a remote target (`issue #3742 <https://github.com/platformio/platformio-core/issues/3742>`_)
+
 5.1.1 (2021-03-17)
 ~~~~~~~~~~~~~~~~~~
 

platformio/commands/test/embedded.py

@@ -117,13 +117,10 @@ class EmbeddedTestProcessor(TestProcessorBase):
                 port = item["port"]
                 for hwid in board_hwids:
                     hwid_str = ("%s:%s" % (hwid[0], hwid[1])).replace("0x", "")
-                    if hwid_str in item["hwid"]:
+                    if hwid_str in item["hwid"] and self.is_serial_port_ready(port):
                         return port
 
-            # check if port is already configured
+            if port and not self.is_serial_port_ready(port):
-            try:
-                serial.Serial(port, timeout=self.SERIAL_TIMEOUT).close()
-            except serial.SerialException:
                 port = None
 
             if not port:
@@ -136,3 +133,18 @@ class EmbeddedTestProcessor(TestProcessorBase):
                 "global `--test-port` option."
             )
         return port
+
+    @staticmethod
+    def is_serial_port_ready(port, timeout=3):
+        if not port:
+            return False
+        elapsed = 0
+        while elapsed < timeout:
+            try:
+                serial.Serial(port, timeout=1).close()
+                return True
+            except:  # pylint: disable=bare-except
+                pass
+            sleep(1)
+            elapsed += 1
+        return False