Python: the rb9704 command line, a fake modem, and the tests

rb9704 drives a 9704 on USB and the Cloudloop account behind it, moved
from WII6's host/rockblock with its project names taken out. rb9704-fake
speaks JSPR on a pty or a serial port: everything the library asks, MO in
segments with the CRC checked, MT, signal, provisioning, refusals and
failures on command.

The tests run against the fake at every level: the fake itself, the
command line, Ground Control's Python binding, the shell sample on
native_sim, and the sample on a board (test_zephyr.py, one suite through
two consoles). test_real.py makes free checks against a real modem.

python/tests/test_library.py

@@ -0,0 +1,56 @@
+"""
+Ground Control's own Python binding (the rockblock9704 package, the same C
+library this repository builds into Zephyr) against the fake modem on a pty.
+The fake runs in a process of its own: the binding holds the GIL through
+every blocking call.
+"""
+
+import time
+
+import pytest
+
+rb = pytest.importorskip("rockblock9704")
+
+
+@pytest.fixture
+def modem(fake):
+    m = rb.RockBlock9704()
+    assert m.begin(fake.port)
+    yield m
+    m.end()
+
+
+def poll_until(m, cond, secs=10):
+    end = time.monotonic() + secs
+    while time.monotonic() < end:
+        m.poll()
+        if cond():
+            return True
+        time.sleep(0.01)
+    return False
+
+
+def test_identity(modem):
+    assert modem.get_imei() == "300434030000000"
+    assert modem.get_iccid() == "8988169712345678901"
+    assert modem.get_firmware_version() == "v1.2.3"
+    assert modem.get_signal() == 5
+
+
+def test_send_async(modem, fake):
+    done = []
+    modem.set_mo_message_complete_callback(lambda mid, status: done.append(status))
+    assert modem.send_message_async(b"from-python", 244)
+    assert poll_until(modem, lambda: done)
+    assert done == [1]
+    m = fake.out.expect(r"^MO 244 \d+ (\w+)")
+    assert bytes.fromhex(m.group(1)) == b"from-python"
+
+
+def test_receive_async(modem, fake):
+    got = []
+    modem.set_mt_message_complete_callback(lambda mid, status: got.append(status))
+    fake.cmd("mt 244 to-python")
+    assert poll_until(modem, lambda: got)
+    assert modem.receive_message_async() == b"to-python"
+    assert modem.acknowledge_receive_head_async()