diff --git a/tests/quick.rs b/tests/quick.rs
index 5829d1c1d..a37b71de7 100644
--- a/tests/quick.rs
+++ b/tests/quick.rs
@@ -258,12 +258,12 @@ where
         let mut it = get_it();
 
         for _ in 0..(counts.len() - 1) {
-            if let None = it.next() {
+            if it.next().is_none() {
                 panic!("Iterator shouldn't be finished, may not be deterministic");
             }
         }
 
-        if let None = it.next() {
+        if it.next().is_none() {
             break 'outer;
         }
 
@@ -438,7 +438,7 @@ quickcheck! {
         }
         assert_eq!(answer, actual);
 
-        assert_eq!(answer.into_iter().last(), a.clone().multi_cartesian_product().last());
+        assert_eq!(answer.into_iter().last(), a.multi_cartesian_product().last());
     }
 
     #[allow(deprecated)]
@@ -498,9 +498,7 @@ quickcheck! {
         exact_size(it)
     }
 
-    fn equal_merge(a: Vec<i16>, b: Vec<i16>) -> bool {
-        let mut sa = a.clone();
-        let mut sb = b.clone();
+    fn equal_merge(mut sa: Vec<i16>, mut sb: Vec<i16>) -> bool {
         sa.sort();
         sb.sort();
         let mut merged = sa.clone();
@@ -517,7 +515,7 @@ quickcheck! {
             exact_size(multizip((a, b, c)))
     }
     fn size_zip_rc(a: Iter<i16>, b: Iter<i16>) -> bool {
-        let rc = rciter(a.clone());
+        let rc = rciter(a);
         correct_size_hint(multizip((&rc, &rc, b)))
     }
 
@@ -526,11 +524,8 @@ quickcheck! {
         correct_size_hint(izip!(filt, b.clone(), c.clone())) &&
             exact_size(izip!(a, b, c))
     }
-    fn equal_kmerge(a: Vec<i16>, b: Vec<i16>, c: Vec<i16>) -> bool {
+    fn equal_kmerge(mut sa: Vec<i16>, mut sb: Vec<i16>, mut sc: Vec<i16>) -> bool {
         use itertools::free::kmerge;
-        let mut sa = a.clone();
-        let mut sb = b.clone();
-        let mut sc = c.clone();
         sa.sort();
         sb.sort();
         sc.sort();
@@ -610,7 +605,7 @@ quickcheck! {
     fn size_2_zip_longest(a: Iter<i16>, b: Iter<i16>) -> bool {
         let it = a.clone().zip_longest(b.clone());
         let jt = a.clone().zip_longest(b.clone());
-        itertools::equal(a.clone(),
+        itertools::equal(a,
                          it.filter_map(|elt| match elt {
                              EitherOrBoth::Both(x, _) => Some(x),
                              EitherOrBoth::Left(x) => Some(x),
@@ -618,7 +613,7 @@ quickcheck! {
                          }
                          ))
             &&
-        itertools::equal(b.clone(),
+        itertools::equal(b,
                          jt.filter_map(|elt| match elt {
                              EitherOrBoth::Both(_, y) => Some(y),
                              EitherOrBoth::Right(y) => Some(y),
@@ -721,7 +716,7 @@ quickcheck! {
 
         assert_eq!(expected_first, curr_perm);
 
-        while let Some(next_perm) = perms.next() {
+        for next_perm in perms {
             assert!(
                 next_perm > curr_perm,
                 "next perm isn't greater-than current; next_perm={:?} curr_perm={:?} n={}",
@@ -943,8 +938,7 @@ quickcheck! {
     fn fuzz_group_by_lazy_1(it: Iter<u8>) -> bool {
         let jt = it.clone();
         let groups = it.group_by(|k| *k);
-        let res = itertools::equal(jt, groups.into_iter().flat_map(|(_, x)| x));
-        res
+        itertools::equal(jt, groups.into_iter().flat_map(|(_, x)| x))
     }
 }
 
@@ -1286,7 +1280,7 @@ quickcheck! {
             .map(|i| (i % modulo, i))
             .into_group_map()
             .into_iter()
-            .map(|(key, vals)| (key, vals.into_iter().fold(0u64, |acc, val| acc + val)))
+            .map(|(key, vals)| (key, vals.into_iter().sum()))
             .collect::<HashMap<_,_>>();
         assert_eq!(lookup, group_map_lookup);
 
@@ -1304,7 +1298,7 @@ quickcheck! {
                 acc + val
             });
 
-        // TODO: Swap `fold1` with stdlib's `fold_first` when it's stabilized
+        #[allow(deprecated)] //TODO: once msrv hits 1.51. replace `fold1` with `reduce`
         let group_map_lookup = a.iter()
             .map(|&b| b as u64)
             .map(|i| (i % modulo, i))
@@ -1551,11 +1545,10 @@ quickcheck! {
 }
 
 quickcheck! {
-    #[test]
     fn counts(nums: Vec<isize>) -> TestResult {
         let counts = nums.iter().counts();
         for (&item, &count) in counts.iter() {
-            if count <= 0 {
+            if count == 0 {
                 return TestResult::failed();
             }
             if count != nums.iter().filter(|&x| x == item).count() {
@@ -1602,7 +1595,7 @@ quickcheck! {
 
 fn is_fused<I: Iterator>(mut it: I) -> bool
 {
-    while let Some(_) = it.next() {}
+    for _ in it.by_ref() {}
     for _ in 0..10{
         if it.next().is_some(){
             return false;
diff --git a/tests/specializations.rs b/tests/specializations.rs
index 199cf562a..057e11c9f 100644
--- a/tests/specializations.rs
+++ b/tests/specializations.rs
@@ -129,7 +129,7 @@ quickcheck! {
             check_results_specialized!(it, |i| {
                 let mut parameters_from_fold = vec![];
                 let fold_result = i.fold(vec![], |mut acc, v| {
-                    parameters_from_fold.push((acc.clone(), v.clone()));
+                    parameters_from_fold.push((acc.clone(), v));
                     acc.push(v);
                     acc
                 });
@@ -139,7 +139,7 @@ quickcheck! {
                 let mut parameters_from_all = vec![];
                 let first = i.next();
                 let all_result = i.all(|x| {
-                    parameters_from_all.push(x.clone());
+                    parameters_from_all.push(x);
                     Some(x)==first
                 });
                 (parameters_from_all, all_result)
diff --git a/tests/test_core.rs b/tests/test_core.rs
index a7b7449d3..38b6014e8 100644
--- a/tests/test_core.rs
+++ b/tests/test_core.rs
@@ -116,7 +116,7 @@ fn chain2() {
 fn write_to() {
     let xs = [7, 9, 8];
     let mut ys = [0; 5];
-    let cnt = ys.iter_mut().set_from(xs.iter().map(|x| *x));
+    let cnt = ys.iter_mut().set_from(xs.iter().copied());
     assert!(cnt == xs.len());
     assert!(ys == [7, 9, 8, 0, 0]);
 
@@ -183,10 +183,7 @@ fn batching() {
     let pit = xs.iter().cloned().batching(|it| {
                match it.next() {
                    None => None,
-                   Some(x) => match it.next() {
-                       None => None,
-                       Some(y) => Some((x, y)),
-                   }
+                   Some(x) => it.next().map(|y| (x, y))
                }
            });
     it::assert_equal(pit, ys.iter().cloned());
@@ -234,7 +231,7 @@ fn count_clones() {
     // Check that RepeatN only clones N - 1 times.
 
     use core::cell::Cell;
-    #[derive(PartialEq, Debug)]
+    #[derive(PartialEq, Eq, Debug)]
     struct Foo {
         n: Cell<usize>
     }
diff --git a/tests/test_std.rs b/tests/test_std.rs
index 4463d912f..f59034234 100644
--- a/tests/test_std.rs
+++ b/tests/test_std.rs
@@ -1,5 +1,3 @@
-use paste;
-use permutohedron;
 use quickcheck as qc;
 use rand::{distributions::{Distribution, Standard}, Rng, SeedableRng, rngs::StdRng};
 use rand::{seq::SliceRandom, thread_rng};
@@ -123,12 +121,12 @@ fn unique() {
 #[test]
 fn intersperse() {
     let xs = ["a", "", "b", "c"];
-    let v: Vec<&str> = xs.iter().map(|x| x.clone()).intersperse(", ").collect();
+    let v: Vec<&str> = xs.iter().cloned().intersperse(", ").collect();
     let text: String = v.concat();
     assert_eq!(text, "a, , b, c".to_string());
 
     let ys = [0, 1, 2, 3];
-    let mut it = ys[..0].iter().map(|x| *x).intersperse(1);
+    let mut it = ys[..0].iter().copied().intersperse(1);
     assert!(it.next() == None);
 }
 
@@ -474,7 +472,7 @@ impl<T: Clone + Send, R: Clone + Rng + SeedableRng + Send> qc::Arbitrary for Ran
 
 // Check that taking the k smallest is the same as
 //  sorting then taking the k first elements
-fn k_smallest_sort<I>(i: I, k: u16) -> ()
+fn k_smallest_sort<I>(i: I, k: u16)
 where
     I: Iterator + Clone,
     I::Item: Ord + Debug,
@@ -538,10 +536,10 @@ fn sorted_by_cached_key() {
 fn test_multipeek() {
     let nums = vec![1u8,2,3,4,5];
 
-    let mp = multipeek(nums.iter().map(|&x| x));
+    let mp = multipeek(nums.iter().copied());
     assert_eq!(nums, mp.collect::<Vec<_>>());
 
-    let mut mp = multipeek(nums.iter().map(|&x| x));
+    let mut mp = multipeek(nums.iter().copied());
     assert_eq!(mp.peek(), Some(&1));
     assert_eq!(mp.next(), Some(1));
     assert_eq!(mp.peek(), Some(&2));
@@ -579,7 +577,7 @@ fn test_multipeek_peeking_next() {
     use crate::it::PeekingNext;
     let nums = vec![1u8,2,3,4,5,6,7];
 
-    let mut mp = multipeek(nums.iter().map(|&x| x));
+    let mut mp = multipeek(nums.iter().copied());
     assert_eq!(mp.peeking_next(|&x| x != 0), Some(1));
     assert_eq!(mp.next(), Some(2));
     assert_eq!(mp.peek(), Some(&3));
@@ -604,10 +602,10 @@ fn test_multipeek_peeking_next() {
 fn test_peek_nth() {
     let nums = vec![1u8,2,3,4,5];
 
-    let iter = peek_nth(nums.iter().map(|&x| x));
+    let iter = peek_nth(nums.iter().copied());
     assert_eq!(nums, iter.collect::<Vec<_>>());
 
-    let mut iter = peek_nth(nums.iter().map(|&x| x));
+    let mut iter = peek_nth(nums.iter().copied());
 
     assert_eq!(iter.peek_nth(0), Some(&1));
     assert_eq!(iter.peek_nth(0), Some(&1));
@@ -638,7 +636,7 @@ fn test_peek_nth() {
 fn test_peek_nth_peeking_next() {
     use it::PeekingNext;
     let nums = vec![1u8,2,3,4,5,6,7];
-    let mut iter = peek_nth(nums.iter().map(|&x| x));
+    let mut iter = peek_nth(nums.iter().copied());
 
     assert_eq!(iter.peeking_next(|&x| x != 0), Some(1));
     assert_eq!(iter.next(), Some(2));
@@ -694,7 +692,7 @@ fn group_by() {
         }
     }
 
-    let toupper = |ch: &char| ch.to_uppercase().nth(0).unwrap();
+    let toupper = |ch: &char| ch.to_uppercase().next().unwrap();
 
     // try all possible orderings
     for indices in permutohedron::Heap::new(&mut [0, 1, 2, 3]) {
@@ -1091,9 +1089,9 @@ fn format() {
     let t2 = format!("{:?}", data.iter().format("--"));
     assert_eq!(t2, ans2);
 
-    let dataf = [1.1, 2.71828, -22.];
+    let dataf = [1.1, 5.71828, -22.];
     let t3 = format!("{:.2e}", dataf.iter().format(", "));
-    assert_eq!(t3, "1.10e0, 2.72e0, -2.20e1");
+    assert_eq!(t3, "1.10e0, 5.72e0, -2.20e1");
 }
 
 #[test]
@@ -1110,7 +1108,7 @@ fn fold_while() {
     let vec = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
     let sum = vec.into_iter().fold_while(0, |acc, item| {
         iterations += 1;
-        let new_sum = acc.clone() + item;
+        let new_sum = acc + item;
         if new_sum <= 20 {
             FoldWhile::Continue(new_sum)
         } else {
@@ -1143,7 +1141,7 @@ fn tree_fold1() {
         "0 1 x 2 3 x x 4 5 x 6 7 x x x 8 9 x 10 11 x x 12 13 x 14 15 x x x x",
     ];
     for (i, &s) in x.iter().enumerate() {
-        let expected = if s == "" { None } else { Some(s.to_string()) };
+        let expected = if s.is_empty() { None } else { Some(s.to_string()) };
         let num_strings = (0..i).map(|x| x.to_string());
         let actual = num_strings.tree_fold1(|a, b| format!("{} {} x", a, b));
         assert_eq!(actual, expected);