test(sdk): add API contract regression tests

Author: catsika

tests/test_contracts.py

@@ -0,0 +1,52 @@
+from unittest.mock import Mock, patch
+
+import pytest
+import requests
+
+from keymint import KeyMint, KeyMintApiError
+
+
+def response(payload, status=200):
+    result = Mock()
+    result.json.return_value = payload
+    result.status_code = status
+    if status >= 400:
+        error = requests.exceptions.HTTPError()
+        error.response = result
+        result.raise_for_status.side_effect = error
+    return result
+
+
+@patch("keymint.requests.get")
+def test_get_key_uses_header_not_query(mock_get):
+    mock_get.return_value = response({"code": 0, "data": {"license": {"productId": "product 123"}}})
+
+    KeyMint("readonly_test").get_key({"productId": "product 123", "licenseKey": "secret/license+key"})
+
+    _, kwargs = mock_get.call_args
+    assert kwargs["params"] == {"productId": "product 123"}
+    assert kwargs["headers"]["x-license-key"] == "secret/license+key"
+    assert "licenseKey" not in kwargs["params"]
+
+
+@patch("keymint.requests.post")
+def test_sign_key_returns_serialized_file(mock_post):
+    mock_post.return_value = response({"file": '{"signedKey":"signature","keyId":"key_123"}'})
+
+    result = KeyMint("admin_test").sign_key({
+        "productId": "product_123", "licenseKey": "license_123", "hostId": "host_123"
+    })
+
+    assert isinstance(result["file"], str)
+
+
+@patch("keymint.requests.post")
+def test_nested_error_preserves_server_message(mock_post):
+    mock_post.return_value = response({
+        "success": False,
+        "error": {"code": "CUSTOMER_EMAIL_EXISTS", "message": "Customer email already exists in team"},
+        "code": 1,
+    }, 409)
+
+    with pytest.raises(KeyMintApiError, match="Customer email already exists in team"):
+        KeyMint("admin_test").create_key({"productId": "product_123"})