Add test

tests/commands/test_startup_time.py

@@ -0,0 +1,14 @@
+import subprocess
+import time
+
+
+MAXIMUM_STARTUP_TIME = 0.5
+
+
+def test_startup_time():
+    start = time.time()
+    subprocess.run(["freqtrade", "-h"])
+    elapsed = time.time() - start
+    assert (
+        elapsed < MAXIMUM_STARTUP_TIME
+    ), "The startup time is too long, try to use lazy import in the command entry function"