Adding pure python highsnr_stdio_P_P_datac0 test.

Intended to replace highsnr_stdio_P_P_datac0 which uses POSIX shell.

test/test_highsnr_stdio_P_P_datac0.py

@@ -0,0 +1,87 @@
+"""
+Tests for the FreeDATA TNC state machine.
+"""
+
+# pylint: disable=global-statement, invalid-name, unused-import
+
+import os
+from re import sub
+import subprocess
+import sys
+
+import pytest
+
+# Replacing:
+#   python3 test_multimode_tx.py --delay 500 --framesperburst ${FRAMESPERBURST} --bursts ${BURSTS} |
+#   python3 test_multimode_rx.py --framesperburst ${FRAMESPERBURST} --bursts ${BURSTS} --timeout 20")
+# with python-controlled subprocesses.
+
+BURSTS = os.environ["BURSTS"]
+FRAMESPERBURST = os.environ["FRAMESPERBURST"]
+
+
+def test_HighSNR_P_P_Multi():
+    """
+    Execute test a high signal-to-noise ratio path.
+
+    :param mycall: Callsign of the near station
+    :type mycall: str
+    :param dxcall: Callsign of the far station
+    :type dxcall: str
+    :return: Bytearray of the requested frame
+    :rtype: bytearray
+    """
+    with subprocess.Popen(
+        args=[
+            "python3",
+            "test_tx.py",
+            "--mode",
+            "datac0",
+            "--delay",
+            "500",
+            "--framesperburst",
+            FRAMESPERBURST,
+            "--bursts",
+            BURSTS,
+        ],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+    ) as transmit:
+
+        with subprocess.Popen(
+            args=[
+                "python3",
+                "test_rx.py",
+                "--mode",
+                "datac0",
+                "--framesperburst",
+                FRAMESPERBURST,
+                "--bursts",
+                BURSTS,
+                "--timeout",
+                "20",
+            ],
+            stdin=transmit.stdout,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+        ) as receive:
+            lastline = "".join(
+                [
+                    str(line, "UTF-8")
+                    for line in receive.stdout.readlines()
+                    if "RECEIVED " in str(line, "UTF-8")
+                ]
+            )
+            assert f"RECEIVED BURSTS: {BURSTS}" in lastline
+            assert f"RECEIVED FRAMES: {int(FRAMESPERBURST) * int(BURSTS)}" in lastline
+            assert "RX_ERRORS: 0" in lastline
+            print(lastline)
+
+
+if __name__ == "__main__":
+    # Run pytest with the current script as the filename.
+    ecode = pytest.main(["-v", "-s", sys.argv[0]])
+    if ecode == 0:
+        print("errors: 0")
+    else:
+        print(ecode)