Fixed wrong test. Now everything is fine.

hw5/task1/src/child/mod.rs

 
             if value > 0 {
                 fork_children(0, value - 1, start_pid);
-            } else {
-                return Err("Number of forks must not be zero.".to_string());
             }
-
             Ok(())
         }
         Err(_) => {

hw5/task1/src/unit_tests.rs

 
     #[test]
     fn test_zero_forks() {
-        assert_eq!(
-            run_childs(123, "0"),
-            Err("Number of forks must not be zero.".to_string())
-        )
+        assert_eq!(run_childs(123, "0"), Ok(()))
     }
 
     #[test]