Add test file

Signed-off-by: Maria Teresa Ortega <teresa.ortega0903@gmail.com>

Author: teresa-ortega

test/core/test_shell.py

@@ -0,0 +1,58 @@
+# Copyright 2026 Ekumen, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unit tests for the shell class in lambkin.core.shell."""
+
+import pytest
+
+from lambkin.core.shell import ShellProxy
+
+
+@pytest.fixture
+def shell():
+    """Return a fresh ShellProxy instance for each test."""
+    return ShellProxy()
+
+
+def test_simple_command(shell, capsys):
+    """Test that a simple single-level command is printed correctly."""
+    shell.ros2.launch("beluga.launch.xml")
+    assert capsys.readouterr().out == "[CMD]: ros2 launch beluga.launch.xml\n"
+
+
+def test_chained_command(shell, capsys):
+    """Test that chained attribute access builds the command word by word."""
+    shell.ros2.bag.play("my_bag")
+    assert capsys.readouterr().out == "[CMD]: ros2 bag play my_bag\n"
+
+
+def test_multiple_args(shell, capsys):
+    """Test that multiple positional arguments are appended in order."""
+    shell.ros2.bag.play("my_bag", "--clock", "-r", "1.0")
+    assert capsys.readouterr().out == "[CMD]: ros2 bag play my_bag --clock -r 1.0\n"
+
+
+def test_kwarg_becomes_flag(shell, capsys):
+    """Test that keyword arguments are converted to --flag value pairs."""
+    shell.evo_ape.bag2("output.mcap", save_results="out.zip")
+    assert (
+        capsys.readouterr().out
+        == "[CMD]: evo_ape bag2 output.mcap --save-results out.zip\n"
+    )
+
+
+def test_arbitrary_tool(shell, capsys):
+    """Test that any top-level tool name works without hardcoding."""
+    shell.evo.traj("output.mcap")
+    assert capsys.readouterr().out == "[CMD]: evo traj output.mcap\n"