test: Add unit test for installing resource limits

This change adds unit test for verifying that the resource limits
for file size and the number of file descriptors has been set
properly.

Signed-off-by: George Siton <geosit@amazon.com>

Author: georgesitoniv

src/jailer/src/resource_limits.rs

@@ -187,4 +187,42 @@ mod tests {
         assert_eq!(rlim.rlim_cur, new_limit);
         assert_eq!(rlim.rlim_max, new_limit);
     }
+
+    #[test]
+    fn test_install() {
+        // Setup the resource limits
+        let mut rlimits = ResourceLimits::default();
+        let new_limit = 100;
+        rlimits.set_file_size(new_limit);
+        rlimits.set_no_file(new_limit);
+        
+        // Install the new limits to file size and 
+        // the number of file descriptors
+        let result = rlimits.install();
+        assert_eq!(result.unwrap(), ());
+    
+        // Verify the new limit for file size
+        let file_size_resource = Resource::RlimitFsize;
+        let mut file_size_limit: libc::rlimit = libc::rlimit {
+            rlim_cur: 0,
+            rlim_max: 0,
+        };
+        unsafe { 
+            libc::getrlimit(file_size_resource.into(), &mut file_size_limit) 
+        };
+        assert_eq!(file_size_limit.rlim_cur, new_limit);
+        assert_eq!(file_size_limit.rlim_max, new_limit);
+
+        // Verify the new limit for the number of file descriptors
+        let file_descriptor_resource = Resource::RlimitNoFile;
+        let mut file_descriptor_limit: libc::rlimit = libc::rlimit {
+            rlim_cur: 0,
+            rlim_max: 0,
+        };
+        unsafe { 
+            libc::getrlimit(file_descriptor_resource.into(), &mut file_descriptor_limit) 
+        };
+        assert_eq!(file_descriptor_limit.rlim_cur, new_limit);
+        assert_eq!(file_descriptor_limit.rlim_max, new_limit);
+    }
 }