pidof: Add test file

tests/by-util/test_pidof.rs

@@ -0,0 +1,11 @@
+// This file is part of the uutils procps package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use crate::common::util::TestScenario;
+
+#[test]
+fn test_invalid_arg() {
+    new_ucmd!().arg("--definitely-invalid").fails().code_is(1);
+}

tests/tests.rs

@@ -32,3 +32,7 @@ mod test_slabtop;
 #[cfg(feature = "pgrep")]
 #[path = "by-util/test_pgrep.rs"]
 mod test_pgrep;
+
+#[cfg(feature = "pidof")]
+#[path = "by-util/test_pidof.rs"]
+mod test_pidof;