test(serial.py): add test for file description leak

pytest-embedded-serial/tests/test_serial.py

@@ -51,3 +51,63 @@ def test_teardown_called_for_multi_dut_succeeded(dut):
 
     result = testdir.runpytest()
     result.assert_outcomes(passed=1, errors=1)
+
+
+def test_serial_file_description_leak(testdir):
+    testdir.makepyfile(r"""
+        import pytest
+        from pytest_lazyfixture import lazy_fixture
+
+
+        dutHelper = None
+
+
+        class DutHelper:
+            def __init__(self):
+                self.duts = None
+
+            def setDut(self, duts):
+                self.duts = duts
+
+            def dut1(self):
+                return self.duts[0]
+
+            def dut2(self):
+                return self.duts[1]
+
+
+        @pytest.fixture
+        def dut_helper(dut):
+            global dutHelper
+            if dutHelper is None:
+                dutHelper = DutHelper()
+            dutHelper.setDut(dut)
+            return dutHelper
+
+
+        @pytest.fixture
+        def DUT1(dut_helper):
+            return dut_helper.dut1()
+
+
+        @pytest.fixture
+        def DUT2(dut_helper):
+            return dut_helper.dut2()
+
+
+        @pytest.mark.parametrize("fixture", [lazy_fixture("DUT1"), lazy_fixture("DUT2")])
+        @pytest.mark.parametrize("test_input", range(0, 300))
+        def test_dummy(test_input, dut, fixture):
+            dut[0].write("foo")
+            assert test_input == test_input
+
+    """)
+
+    result = testdir.runpytest(
+        '-s',
+        '--count', 2,
+        '--embedded-services', 'serial|serial',
+        '--port',  '/dev/ttyUSB0|/dev/ttyUSB1',
+        '--baud', '115200|115200'
+    )
+    result.assert_outcomes(passed=600)