test: add test_cli_smoke (#16)

to improve coverage

Author: bcdady

tests/test_cli.py

@@ -0,0 +1,10 @@
+import subprocess, sys, json
+
+def test_cli_smoke():
+    result = subprocess.run(
+        [sys.executable, "-m", "tfsumpy", "--help"],
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+    assert "usage" in result.stdout.lower()