diff --git a/tests/specializations.rs b/tests/specializations.rs
index 8f3805c34..dc3ff6a8a 100644
--- a/tests/specializations.rs
+++ b/tests/specializations.rs
@@ -15,16 +15,16 @@ where
     }
 }
 
-fn check_specialized<'a, V, IterItem, Iter, F>(iterator: &Iter, mapper: F)
-where
-    V: Eq + Debug,
-    Iter: Iterator<Item = IterItem> + Clone + 'a,
-    F: Fn(Box<dyn Iterator<Item = IterItem> + 'a>) -> V,
-{
-    assert_eq!(
-        mapper(Box::new(Unspecialized(iterator.clone()))),
-        mapper(Box::new(iterator.clone()))
-    )
+macro_rules! check_specialized {
+    ($src:expr, |$it:pat| $closure:expr) => {
+        let $it = $src.clone();
+        let v1 = $closure;
+
+        let $it = Unspecialized($src.clone());
+        let v2 = $closure;
+
+        assert_eq!(v1, v2);
+    }
 }
 
 fn test_specializations<IterItem, Iter>(
@@ -33,10 +33,10 @@ fn test_specializations<IterItem, Iter>(
     IterItem: Eq + Debug + Clone,
     Iter: Iterator<Item = IterItem> + Clone,
 {
-    check_specialized(it, |i| i.count());
-    check_specialized(it, |i| i.last());
-    check_specialized(it, |i| i.collect::<Vec<_>>());
-    check_specialized(it, |i| {
+    check_specialized!(it, |i| i.count());
+    check_specialized!(it, |i| i.last());
+    check_specialized!(it, |i| i.collect::<Vec<_>>());
+    check_specialized!(it, |i| {
         let mut parameters_from_fold = vec![];
         let fold_result = i.fold(vec![], |mut acc, v: IterItem| {
             parameters_from_fold.push((acc.clone(), v.clone()));
@@ -45,7 +45,7 @@ fn test_specializations<IterItem, Iter>(
         });
         (parameters_from_fold, fold_result)
     });
-    check_specialized(it, |mut i| {
+    check_specialized!(it, |mut i| {
         let mut parameters_from_all = vec![];
         let first = i.next();
         let all_result = i.all(|x| {
@@ -56,7 +56,7 @@ fn test_specializations<IterItem, Iter>(
     });
     let size = it.clone().count();
     for n in 0..size + 2 {
-        check_specialized(it, |mut i| i.nth(n));
+        check_specialized!(it, |mut i| i.nth(n));
     }
     // size_hint is a bit harder to check
     let mut it_sh = it.clone();