fixup! factor: Add test exhibiting a bug in ρ

src/uu/factor/src/factor.rs

@@ -159,8 +159,13 @@ mod tests {
 
     #[test]
     fn factor_recombines_strong_pseudoprime() {
+        // This is a strong pseudoprime (wrt. miller_rabin::BASIS)
+        //  and triggered a bug in rho::factor's codepath handling
+        //  miller_rabbin::Result::Composite
         let pseudoprime = 17179869183;
         for _ in 0..20 {
+            // Repeat the test 20 times, as it only fails some fraction
+            // of the time.
             assert!(factor(pseudoprime).product() == pseudoprime);
         }
     }