diff --git a/tests/test_config_validate.py b/tests/test_config_validate.py
new file mode 100644
index 00000000..441d45fc
--- /dev/null
+++ b/tests/test_config_validate.py
@@ -0,0 +1,72 @@
+"""Tests for config validation (#690)."""
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from scripts.config_validate import validate_config, ValidationError
+
+
+def test_valid_config():
+    content = "model: gpt-4\nprovider: openai\n"
+    valid, errors = validate_config(content)
+    assert valid
+    assert len(errors) == 0
+
+
+def test_missing_required_key():
+    content = "provider: openai\n"
+    valid, errors = validate_config(content)
+    assert not valid
+    assert any("model" in e.path for e in errors)
+
+
+def test_wrong_type():
+    content = "model: 123\n"
+    valid, errors = validate_config(content)
+    assert not valid
+    assert any("model" in e.path for e in errors)
+
+
+def test_forbidden_key():
+    content = "model: gpt-4\npassword: secret123\n"
+    valid, errors = validate_config(content)
+    assert not valid
+    assert any("password" in e.path for e in errors)
+
+
+def test_invalid_yaml():
+    content = "model: gpt-4\n  bad indentation\n"
+    valid, errors = validate_config(content)
+    assert not valid
+
+
+def test_nested_validation():
+    content = "model: gpt-4\nagent:\n  max_turns: not_a_number\n"
+    valid, errors = validate_config(content)
+    assert not valid
+    assert any("max_turns" in e.path for e in errors)
+
+
+def test_toolsets_validation():
+    content = "model: gpt-4\ntoolsets:\n  - web\n  - 123\n"
+    valid, errors = validate_config(content)
+    assert not valid
+
+
+def test_empty_file():
+    content = ""
+    valid, errors = validate_config(content)
+    assert not valid
+
+
+if __name__ == "__main__":
+    tests = [test_valid_config, test_missing_required_key, test_wrong_type,
+             test_forbidden_key, test_invalid_yaml, test_nested_validation,
+             test_toolsets_validation, test_empty_file]
+    for t in tests:
+        print(f"Running {t.__name__}...")
+        t()
+        print("  PASS")
+    print("\nAll tests passed.")