Add test to verify clap argument parser.

Bug: 260823636
Test: atest prng_seeder.test
Change-Id: I2e69fa662c9f96b367ae27f640b4687da22ca8ac
diff --git a/prng_seeder/src/main.rs b/prng_seeder/src/main.rs
index 3f698f6..924481a 100644
--- a/prng_seeder/src/main.rs
+++ b/prng_seeder/src/main.rs
@@ -37,7 +37,7 @@
 
 use crate::conditioner::ConditionerBuilder;
 
-#[derive(Debug, clap::Parser)]
+#[derive(Debug, Parser)]
 struct Cli {
     #[clap(long, default_value = "/dev/hw_random")]
     source: PathBuf,
@@ -135,3 +135,14 @@
     println!("prng_seeder: launch terminated: {:?}", e);
     std::process::exit(-1);
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use clap::CommandFactory;
+
+    #[test]
+    fn verify_cli() {
+        Cli::command().debug_assert();
+    }
+}