🧪 Add comprehensive unit tests for portfolio config validation

Implemented `tests/portfolio/test_config.py` to test the `validate_config` function in `tradingagents/portfolio/config.py`.

Key improvements:
- Added `test_validate_config_max_positions_invalid` to verify `max_positions` boundary conditions (0, -1).
- Added happy path test `test_validate_config_valid`.
- Added tests for `max_position_pct`, `max_sector_pct`, `min_cash_pct`, and `default_budget` validation.
- Verified that tests correctly catch bugs by temporarily disabling validation logic.

These tests ensure the portfolio manager configuration is robustly validated before use.

Co-authored-by: aguzererler <6199053+aguzererler@users.noreply.github.com>

tests/portfolio/test_config.py

@@ -0,0 +1,104 @@
+"""Tests for tradingagents/portfolio/config.py."""
+
+import pytest
+from tradingagents.portfolio.config import validate_config
+
+def test_validate_config_valid():
+    """Happy path: valid configuration."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    # Should not raise any exception
+    validate_config(cfg)
+
+def test_validate_config_max_positions_invalid():
+    """max_positions must be >= 1."""
+    cfg = {
+        "max_positions": 0,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"max_positions must be >= 1"):
+        validate_config(cfg)
+
+    cfg["max_positions"] = -1
+    with pytest.raises(ValueError, match=r"max_positions must be >= 1"):
+        validate_config(cfg)
+
+def test_validate_config_max_position_pct_invalid():
+    """max_position_pct must be in (0, 1]."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.0,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"max_position_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+    cfg["max_position_pct"] = 1.1
+    with pytest.raises(ValueError, match=r"max_position_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+def test_validate_config_max_sector_pct_invalid():
+    """max_sector_pct must be in (0, 1]."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.0,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"max_sector_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+    cfg["max_sector_pct"] = 1.1
+    with pytest.raises(ValueError, match=r"max_sector_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+def test_validate_config_min_cash_pct_invalid():
+    """min_cash_pct must be in [0, 1)."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": -0.1,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"min_cash_pct must be in \[0, 1\)"):
+        validate_config(cfg)
+
+    cfg["min_cash_pct"] = 1.0
+    with pytest.raises(ValueError, match=r"min_cash_pct must be in \[0, 1\)"):
+        validate_config(cfg)
+
+def test_validate_config_default_budget_invalid():
+    """default_budget must be > 0."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 0.0
+    }
+    with pytest.raises(ValueError, match=r"default_budget must be > 0"):
+        validate_config(cfg)
+
+def test_validate_config_sum_constraints_invalid():
+    """min_cash_pct + max_position_pct must be <= 1.0."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.6,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.5,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"must be <= 1.0"):
+        validate_config(cfg)