set up testing

tests/test_smoke_test.py

@@ -0,0 +1,10 @@
+from click.testing import CliRunner
+
+from xexe.cli import smoke_test
+
+
+def test_smoke_test():
+    runner = CliRunner()
+    result = runner.invoke(smoke_test)
+    assert result.exit_code == 0
+    assert "Oink oink!" in result.output