Per #175, check for duplicate devices. I am comparing slugs, and found a duplicate Generic device already.

device-types/Generic/shelf-2he.yaml

@@ -1,6 +1,6 @@
 manufacturer: Generic
-model: shelf-1he
-slug: shelf-1he
+model: shelf-2he
+slug: shelf-2he
 u_height: 2
 full_depth: false
 

tests/test_dupes.py

@@ -0,0 +1,41 @@
+import glob
+import json
+import pytest
+import yaml
+
+KNOWN_MODELS = {}
+
+def _get_definition_files():
+    """
+    Return a list of all definition files.
+    """
+    return [f for f in glob.glob("device-types/*/*", recursive=True)]
+
+def test_environment():
+    """
+    Run basic sanity checks on the environment to ensure tests are running correctly.
+    """
+    # Validate that definition files exist
+    assert _get_definition_files(), "No definition files found!"
+
+@pytest.mark.parametrize("file_path", _get_definition_files())
+def test_dupes(file_path):
+    # Check file extension
+    assert file_path.split('.')[-1] in ('yaml', 'yml'), f"Invalid file extension: {file_path}"
+
+    # Read file
+    with open(file_path) as definition_file:
+        content = definition_file.read()
+
+        # Check for trailing newline
+        assert content[-1] == '\n', "Missing trailing newline"
+
+        # Load YAML data
+        definition = yaml.load(content, Loader=yaml.SafeLoader)
+
+    slug = definition.get('slug')
+
+    if KNOWN_MODELS.get(slug, None) is not None:
+        pytest.fail(f"{file_path} is a duplicate device_type for {slug}")
+
+    KNOWN_MODELS[slug] = definition.get('model')