[Add] added a test to check if all module can be import without error.

tests/load_all.py

@@ -0,0 +1,26 @@
+# flake8: noqa
+import unittest
+
+
+class ImportTest(unittest.TestCase):
+
+    # noinspection PyUnresolvedReferences
+    def test_import_all(self):
+        from vnpy.event import EventEngine
+
+        from vnpy.trader.engine import MainEngine
+        from vnpy.trader.ui import MainWindow, create_qapp
+
+        from vnpy.gateway.bitmex import BitmexGateway
+        from vnpy.gateway.futu import FutuGateway
+        from vnpy.gateway.ib import IbGateway
+        from vnpy.gateway.ctp import CtpGateway
+        from vnpy.gateway.tiger import TigerGateway
+        from vnpy.gateway.oes import OesGateway
+
+        from vnpy.app.cta_strategy import CtaStrategyApp
+        from vnpy.app.csv_loader import CsvLoaderApp
+
+
+if __name__ == '__main__':
+    unittest.main()