test: add pytest and test config load/migrate (MR 2252)

re-introduce pytest, add a conftest.py with some useful fixtures and
basic tests for config loading.

This just checks that we can load the config and migrate it from the old
2.3.x format to the new 3.0 format with the new mirrors section.

Testing anything that requires args or Context should probably wait
until we can properly model state (since global state like in
get_context() really doesn't jive with pytest).

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

pmb/conftest.py

@@ -0,0 +1,103 @@
+import os
+from pathlib import Path
+import pytest
+from contextlib import contextmanager
+
+@contextmanager
+def _fixture_context(val):
+    yield val
+
+@pytest.fixture(scope="session")
+def config_file_session(tmp_path_factory):
+    """Fixture to create a temporary pmbootstrap.cfg file."""
+    tmp_path = tmp_path_factory.mktemp("pmbootstrap")
+    file = tmp_path / "pmbootstrap.cfg"
+    workdir = tmp_path / "work"
+    workdir.mkdir()
+    contents = """[pmbootstrap]
+build_default_device_arch = True
+ccache_size = 5G
+device = qemu-amd64
+extra_packages = neofetch,neovim,reboot-mode
+hostname = qemu-amd64
+is_default_channel = False
+jobs = 8
+kernel = edge
+locale = C.UTF-8
+ssh_keys = True
+sudo_timer = True
+systemd = always
+timezone = Europe/Berlin
+ui = gnome
+work = {0}
+
+[providers]
+
+[mirrors]
+""".format(workdir)
+
+    open(file, "w").write(contents)
+    return file
+
+
+@pytest.fixture
+def config_file(config_file_session):
+    """Fixture to create a temporary pmbootstrap.cfg file."""
+    with _fixture_context(config_file_session) as val:
+        yield val
+
+
+@pytest.fixture(autouse=True)
+def setup_logging(tmp_path: Path):
+    """Setup logging for all tests."""
+    import logging
+    logfile = tmp_path / "test.log"
+    logging.basicConfig(level=logging.DEBUG, force=True, filename=logfile)
+
+
+@pytest.fixture(autouse=True)
+def setup_mock_ask(monkeypatch):
+    """Common setup to mock cli.ask() to avoid reading from stdin"""
+    import pmb.helpers.cli
+
+    def mock_ask(question="Continue?", choices=["y", "n"], default="n",
+                 lowercase_answer=True, validation_regex=None, complete=None):
+        return default
+
+    monkeypatch.setattr(pmb.helpers.cli, "ask", mock_ask)
+
+
+# FIXME: get_context() at runtime somehow doesn't return the
+# custom context we set up here.
+# @pytest.fixture(scope="session")
+# def pmb_args(config_file_session):
+#     """This is (still) a hack, since a bunch of the codebase still
+#     expects some global state to be initialised. We do that here."""
+
+#     from pmb.types import PmbArgs
+#     from pmb.helpers.args import init as init_args
+
+#     args = PmbArgs()
+#     args.config = config_file_session
+#     args.aports = None
+#     args.timeout = 900
+#     args.details_to_stdout = False
+#     args.quiet = False
+#     args.verbose = False
+#     args.offline = False
+#     args.action = "init"
+#     args.cross = False
+#     args.log = Path()
+
+#     print("init_args")
+#     return init_args(args)
+
+@pytest.fixture
+def foreign_arch():
+    """Fixture to return the foreign arch."""
+    from pmb.core.arch import Arch
+    if os.uname().machine == "x86_64":
+        return Arch.aarch64
+
+    return Arch.x86_64
+