Add CLI end-to-end tests

Currently there don't seem to be any way to test the CLI commands.
Since this change mostly happens in those I thought it best to add
a way to test these commands end-to-end.

More integrated commands like `lerobot-record` need patching but
standalone commands like training seem to work fine.

tests/test_cli.py

@@ -0,0 +1,137 @@
+import importlib
+from unittest.mock import patch
+
+import pytest
+from safetensors.torch import load_file
+
+
+def run_command(cmd, module, args):
+    module = importlib.import_module(f"lerobot.scripts.{module}")
+    with patch("sys.argv", [cmd] + args):
+        module.main()
+
+
+def lerobot_train(args):
+    return run_command(cmd="lerobot-train", module="lerobot_train", args=args)
+
+
+def lerobot_record(args):
+    return run_command(cmd="lerobot-record", module="lerobot_record", args=args)
+
+
+@pytest.mark.parametrize("policy_type", ["smolvla"])
+def test_peft_training_works(policy_type, tmp_path):
+    """Check whether the standard case of fine-tuning a (partially) pre-trained policy with PEFT works."""
+    output_dir = tmp_path / f"output_{policy_type}"
+
+    lerobot_train(
+        [
+            f"--policy.type={policy_type}",
+            "--policy.push_to_hub=false",
+            "--peft.method=LORA",
+            "--dataset.repo_id=lerobot/pusht",
+            "--dataset.episodes=[0, 1]",
+            "--steps=1",
+            f"--output_dir={output_dir}",
+        ]
+    )
+
+    policy_dir = output_dir / "checkpoints" / "last" / "pretrained_model"
+
+    for file in ["adapter_config.json", "adapter_model.safetensors", "config.json"]:
+        assert (policy_dir / file).exists()
+
+    # This is the default case where we train a pre-trained policy from scratch with new data.
+    # We assume that we target policy-specific modules but fully fine-tune action and state projections
+    # so these must be part of the trained state dict.
+    state_dict = load_file(policy_dir / "adapter_model.safetensors")
+
+    fully_trained_keys = [
+        "state_proj",
+        "action_in_proj",
+        "action_out_proj",
+        "action_time_mlp_in",
+        "action_time_mlp_out",
+    ]
+
+    found_keys = [
+        module_key
+        for module_key in fully_trained_keys
+        for state_dict_key in state_dict
+        if f".{module_key}." in state_dict_key
+    ]
+
+    assert set(found_keys) == set(fully_trained_keys)
+
+
+class DummyRobot:
+    name = "dummy"
+    cameras = []
+    action_features = {"foo": 1.0, "bar": 2.0}
+    observation_features = {"obs1": 1.0, "obs2": 2.0}
+
+    def connect(self, *args):
+        pass
+
+    def disconnect(self):
+        pass
+
+
+def dummy_make_robot_from_config(*args, **kwargs):
+    return DummyRobot()
+
+
+@pytest.mark.parametrize("policy_type", ["smolvla"])
+def test_peft_record_loads_policy(policy_type, tmp_path):
+    """Train a policy with PEFT and attempt to load it with `lerobot-record`."""
+    from peft import PeftModel
+
+    output_dir = tmp_path / f"output_{policy_type}"
+
+    lerobot_train(
+        [
+            f"--policy.type={policy_type}",
+            "--policy.push_to_hub=false",
+            "--peft.method=LORA",
+            "--dataset.repo_id=lerobot/pusht",
+            "--dataset.episodes=[0, 1]",
+            "--steps=1",
+            f"--output_dir={output_dir}",
+        ]
+    )
+
+    policy_dir = output_dir / "checkpoints" / "last" / "pretrained_model"
+    dataset_dir = tmp_path / "eval_pusht"
+    single_task = "move the table"
+    loaded_policy = None
+
+    def dummy_record_loop(*args, **kwargs):
+        nonlocal loaded_policy
+
+        if "dataset" not in kwargs:
+            return
+
+        dataset = kwargs["dataset"]
+        dataset.add_frame({"task": single_task})
+        loaded_policy = kwargs["policy"]
+
+    with (
+        patch("lerobot.robots.make_robot_from_config", dummy_make_robot_from_config),
+        # disable record loop since we're only interested in successful loading of the policy.
+        patch("lerobot.scripts.lerobot_record.record_loop", dummy_record_loop),
+        # disable speech output
+        patch("lerobot.utils.utils.say"),
+    ):
+        lerobot_record(
+            [
+                f"--policy.path={policy_dir}",
+                "--robot.type=so101_follower",
+                "--robot.port=/dev/null",
+                "--dataset.repo_id=lerobot/eval_pusht",
+                f'--dataset.single_task="{single_task}"',
+                f"--dataset.root={dataset_dir}",
+                "--dataset.push_to_hub=false",
+            ]
+        )
+
+        assert isinstance(loaded_policy, PeftModel)