🧪 Add unit tests for format_bytes utility function

- Created tests/test_vram_node.py
- Mocked dependencies (torch, comfy) to allow testing in isolation
- Implemented test cases for zero values, exact GB, fractional values, small values (rounding check), and large values.
- Verified test robustness by confirming failure when logic was intentionally altered.

tests/test_vram_node.py

@@ -0,0 +1,55 @@
+import sys
+import types
+import pytest
+from unittest.mock import MagicMock
+import os
+
+# Mock dependencies before importing anything that might depend on them
+mock_torch = types.ModuleType("torch")
+mock_torch.cuda = MagicMock()
+mock_torch.cuda.is_available.return_value = False
+sys.modules["torch"] = mock_torch
+
+sys.modules["comfy"] = types.ModuleType("comfy")
+sys.modules["comfy.model_management"] = types.ModuleType("comfy.model_management")
+
+def get_format_bytes():
+    # Read the file
+    vram_node_path = os.path.join(os.path.dirname(__file__), "..", "vram_node.py")
+    with open(vram_node_path, 'r') as f:
+        code = f.read()
+
+    # Mock 'from . import register_node' by replacing it
+    code = code.replace("from . import register_node", "def register_node(c, *args, **kwargs): return c")
+
+    vram_module = types.ModuleType("vram_node")
+    exec(code, vram_module.__dict__)
+
+    return vram_module.format_bytes
+
+@pytest.fixture
+def format_bytes():
+    return get_format_bytes()
+
+def test_format_bytes_zero(format_bytes):
+    assert format_bytes(0) == "0.00 GB"
+
+def test_format_bytes_gigabyte(format_bytes):
+    assert format_bytes(1024**3) == "1.00 GB"
+
+def test_format_bytes_fractional(format_bytes):
+    assert format_bytes(1024**3 * 0.5) == "0.50 GB"
+    assert format_bytes(1024**3 * 2.5) == "2.50 GB"
+
+def test_format_bytes_small_values(format_bytes):
+    # 1 MB is 1/1024 GB ≈ 0.000976 GB -> 0.00 GB
+    assert format_bytes(1024**2) == "0.00 GB"
+    # 10 MB is 10/1024 GB ≈ 0.009765 GB -> 0.01 GB (due to rounding .2f)
+    assert format_bytes(1024**2 * 10) == "0.01 GB"
+
+def test_format_bytes_large_values(format_bytes):
+    assert format_bytes(1024**3 * 1024) == "1024.00 GB"
+    assert format_bytes(1024**3 * 123.456) == "123.46 GB"
+
+if __name__ == "__main__":
+    pytest.main([__file__])