diff --git a/src/lib.rs b/src/lib.rs
index 0431c52..2369b42 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -24,3 +24,4 @@ pub mod p21_merge_two_sorted_lists;
 pub mod p22_generate_parentheses;
 pub mod p23_merge_k_sorted_lists;
 pub mod p24_swap_nodes_in_pairs;
+pub mod p25_reverse_nodes_in_k_group;
diff --git a/src/p10_regular_expression_matching.rs b/src/p10_regular_expression_matching.rs
index 15a54d7..acd3d9a 100644
--- a/src/p10_regular_expression_matching.rs
+++ b/src/p10_regular_expression_matching.rs
@@ -18,17 +18,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::is_match("aa".to_string(), "a".to_string()), false);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::is_match("aa".to_string(), "a*".to_string()), true);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::is_match("aa".to_string(), "a".to_string()), false);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::is_match("ab".to_string(), ".*".to_string()), true);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::is_match("aa".to_string(), "a*".to_string()), true);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::is_match("ab".to_string(), ".*".to_string()), true);
+    }
 }
diff --git a/src/p11_container_with_most_water.rs b/src/p11_container_with_most_water.rs
index 8d0a4d8..6412404 100644
--- a/src/p11_container_with_most_water.rs
+++ b/src/p11_container_with_most_water.rs
@@ -18,12 +18,17 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::max_area(vec![1,8,6,2,5,4,8,3,7]), 49);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::max_area(vec![1,1]), 1);
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::max_area(vec![1,8,6,2,5,4,8,3,7]), 49);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::max_area(vec![1,1]), 1);
+    }
 }
diff --git a/src/p12_integer_to_roman.rs b/src/p12_integer_to_roman.rs
index 7db55c3..4d6de0d 100644
--- a/src/p12_integer_to_roman.rs
+++ b/src/p12_integer_to_roman.rs
@@ -33,17 +33,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::int_to_roman(3), "III");
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::int_to_roman(58), "LVIII");
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::int_to_roman(3), "III");
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::int_to_roman(1994), "MCMXCIV");
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::int_to_roman(58), "LVIII");
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::int_to_roman(1994), "MCMXCIV");
+    }
 }
diff --git a/src/p13_roman_to_integer.rs b/src/p13_roman_to_integer.rs
index 2553427..96a21b1 100644
--- a/src/p13_roman_to_integer.rs
+++ b/src/p13_roman_to_integer.rs
@@ -11,17 +11,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::roman_to_int("III".to_string()), 3);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::roman_to_int("LVIII".to_string()), 58);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::roman_to_int("III".to_string()), 3);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::roman_to_int("MCMXCIV".to_string()), 1994);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::roman_to_int("LVIII".to_string()), 58);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::roman_to_int("MCMXCIV".to_string()), 1994);
+    }
 }
diff --git a/src/p14_longest_common_prefix.rs b/src/p14_longest_common_prefix.rs
index 4346b90..3fe03d8 100644
--- a/src/p14_longest_common_prefix.rs
+++ b/src/p14_longest_common_prefix.rs
@@ -17,14 +17,19 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    let strs = vec!["flower".to_string(),"flow".to_string(),"flight".to_string()];
-    assert_eq!(Solution::longest_common_prefix(strs), "fl");
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    let strs = vec!["dog".to_string(),"racecar".to_string(),"car".to_string()];
-    assert_eq!(Solution::longest_common_prefix(strs), "");
+    #[test]
+    fn test1() {
+        let strs = vec!["flower".to_string(),"flow".to_string(),"flight".to_string()];
+        assert_eq!(Solution::longest_common_prefix(strs), "fl");
+    }
+
+    #[test]
+    fn test2() {
+        let strs = vec!["dog".to_string(),"racecar".to_string(),"car".to_string()];
+        assert_eq!(Solution::longest_common_prefix(strs), "");
+    }
 }
diff --git a/src/p15_3sum.rs b/src/p15_3sum.rs
index b3e30ab..c8adb3e 100644
--- a/src/p15_3sum.rs
+++ b/src/p15_3sum.rs
@@ -28,17 +28,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::three_sum(vec![-1,0,1,2,-1,-4]), vec![vec![-1,-1,2], vec![-1,0,1]]);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::three_sum(vec![0,1,1]), Vec::<Vec<i32>>::new());
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::three_sum(vec![-1,0,1,2,-1,-4]), vec![vec![-1,-1,2], vec![-1,0,1]]);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::three_sum(vec![0,0,0]), vec![vec![0,0,0]]);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::three_sum(vec![0,1,1]), Vec::<Vec<i32>>::new());
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::three_sum(vec![0,0,0]), vec![vec![0,0,0]]);
+    }
 }
\ No newline at end of file
diff --git a/src/p16_3sum_closest.rs b/src/p16_3sum_closest.rs
index 1d89769..f556e8c 100644
--- a/src/p16_3sum_closest.rs
+++ b/src/p16_3sum_closest.rs
@@ -22,12 +22,17 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::three_sum_closest(vec![-1,2,1,-4], 1), 2);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::three_sum_closest(vec![0,0,0], 1), 0);
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::three_sum_closest(vec![-1,2,1,-4], 1), 2);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::three_sum_closest(vec![0,0,0], 1), 0);
+    }
 }
diff --git a/src/p17_letter_combinations_of_a_phone_number.rs b/src/p17_letter_combinations_of_a_phone_number.rs
index 6e99723..38b24c3 100644
--- a/src/p17_letter_combinations_of_a_phone_number.rs
+++ b/src/p17_letter_combinations_of_a_phone_number.rs
@@ -23,19 +23,24 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    let mut actual = Solution::letter_combinations("23".to_string());
-    actual.sort();
-    assert_eq!(actual, vec!["ad","ae","af","bd","be","bf","cd","ce","cf"]);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::letter_combinations(String::new()), Vec::<String>::new());
-}
+    #[test]
+    fn test1() {
+        let mut actual = Solution::letter_combinations("23".to_string());
+        actual.sort();
+        assert_eq!(actual, vec!["ad","ae","af","bd","be","bf","cd","ce","cf"]);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::letter_combinations("2".to_string()), vec!["a","b","c"]);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::letter_combinations(String::new()), Vec::<String>::new());
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::letter_combinations("2".to_string()), vec!["a","b","c"]);
+    }
 }
diff --git a/src/p18_4sum.rs b/src/p18_4sum.rs
index 67fe639..7846f17 100644
--- a/src/p18_4sum.rs
+++ b/src/p18_4sum.rs
@@ -35,21 +35,26 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    let mut actual = Solution::four_sum(vec![1,0,-1,0,-2,2], 0);
-    actual.iter_mut().for_each(|v| v.sort());
-    assert_eq!(actual, vec![
-        vec![-2,-1,1,2], vec![-2,0,0,2], vec![-1,0,0,1]
-    ]);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::four_sum(vec![2,2,2,2,2], 8), vec![vec![2,2,2,2]]);
-}
+    #[test]
+    fn test1() {
+        let mut actual = Solution::four_sum(vec![1,0,-1,0,-2,2], 0);
+        actual.iter_mut().for_each(|v| v.sort());
+        assert_eq!(actual, vec![
+            vec![-2,-1,1,2], vec![-2,0,0,2], vec![-1,0,0,1]
+        ]);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::four_sum(vec![1000000000,1000000000,1000000000,1000000000], -294967296), Vec::<Vec<i32>>::new());
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::four_sum(vec![2,2,2,2,2], 8), vec![vec![2,2,2,2]]);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::four_sum(vec![1000000000,1000000000,1000000000,1000000000], -294967296), Vec::<Vec<i32>>::new());
+    }
 }
diff --git a/src/p19_remove_nth_node_from_end_of_list.rs b/src/p19_remove_nth_node_from_end_of_list.rs
index 9d8ba5d..4da02bb 100644
--- a/src/p19_remove_nth_node_from_end_of_list.rs
+++ b/src/p19_remove_nth_node_from_end_of_list.rs
@@ -22,22 +22,28 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::remove_nth_from_end(list![1,2,3,4,5], 2), list![1,2,3,5]);
-}
+#[cfg(test)]
+mod tests {
+    use crate::linked_list::ListNode;
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::remove_nth_from_end(list![1], 1), list![]);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::remove_nth_from_end(list![1,2,3,4,5], 2), list![1,2,3,5]);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::remove_nth_from_end(list![1,2], 1), list![1]);
-}
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::remove_nth_from_end(list![1], 1), list![]);
+    }
 
-#[test]
-fn test4() {
-    assert_eq!(Solution::remove_nth_from_end(list![1,2], 2), list![2]);
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::remove_nth_from_end(list![1,2], 1), list![1]);
+    }
+
+    #[test]
+    fn test4() {
+        assert_eq!(Solution::remove_nth_from_end(list![1,2], 2), list![2]);
+    }
 }
diff --git a/src/p1_two_sum.rs b/src/p1_two_sum.rs
index 2b3d484..9504b15 100644
--- a/src/p1_two_sum.rs
+++ b/src/p1_two_sum.rs
@@ -15,21 +15,25 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    let actual = Solution::two_sum(vec![2,7,11,15], 9);
-    assert!(actual == vec![1,0] || actual == vec![0,1]);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    let actual = Solution::two_sum(vec![3,2,4], 6);
-    assert!(actual == vec![1,2] || actual == vec![2,1]);
-}
+    #[test]
+    fn test1() {
+        let actual = Solution::two_sum(vec![2,7,11,15], 9);
+        assert!(actual == vec![1,0] || actual == vec![0,1]);
+    }
 
-#[test]
-fn test3() {
-    let actual = Solution::two_sum(vec![3,3], 6);
-    assert!(actual == vec![1,0] || actual == vec![0,1]);
+    #[test]
+    fn test2() {
+        let actual = Solution::two_sum(vec![3,2,4], 6);
+        assert!(actual == vec![1,2] || actual == vec![2,1]);
+    }
+
+    #[test]
+    fn test3() {
+        let actual = Solution::two_sum(vec![3,3], 6);
+        assert!(actual == vec![1,0] || actual == vec![0,1]);
+    }
 }
-    
\ No newline at end of file
diff --git a/src/p20_valid_parentheses.rs b/src/p20_valid_parentheses.rs
index 228265c..1286244 100644
--- a/src/p20_valid_parentheses.rs
+++ b/src/p20_valid_parentheses.rs
@@ -20,17 +20,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::is_valid("()".to_string()), true);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::is_valid("()[]{}".to_string()), true);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::is_valid("()".to_string()), true);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::is_valid("(]".to_string()), false);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::is_valid("()[]{}".to_string()), true);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::is_valid("(]".to_string()), false);
+    }
 }
diff --git a/src/p21_merge_two_sorted_lists.rs b/src/p21_merge_two_sorted_lists.rs
index 55cd7cf..297f9b7 100644
--- a/src/p21_merge_two_sorted_lists.rs
+++ b/src/p21_merge_two_sorted_lists.rs
@@ -27,17 +27,23 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::merge_two_lists(list![1,2,4], list![1,3,4]), list![1,1,2,3,4,4]);
-}
+#[cfg(test)]
+mod tests {
+    use crate::linked_list::ListNode;
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::merge_two_lists(list![], list![]), list![]);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::merge_two_lists(list![1,2,4], list![1,3,4]), list![1,1,2,3,4,4]);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::merge_two_lists(list![], list![0]), list![0]);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::merge_two_lists(list![], list![]), list![]);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::merge_two_lists(list![], list![0]), list![0]);
+    }
 }
diff --git a/src/p22_generate_parentheses.rs b/src/p22_generate_parentheses.rs
index 2918f4a..7abf682 100644
--- a/src/p22_generate_parentheses.rs
+++ b/src/p22_generate_parentheses.rs
@@ -15,14 +15,19 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    let mut actual = Solution::generate_parenthesis(3);
-    actual.sort();
-    assert_eq!(actual, vec!["((()))","(()())","(())()","()(())","()()()"]);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::generate_parenthesis(1), vec!["()"]);
+    #[test]
+    fn test1() {
+        let mut actual = Solution::generate_parenthesis(3);
+        actual.sort();
+        assert_eq!(actual, vec!["((()))","(()())","(())()","()(())","()()()"]);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::generate_parenthesis(1), vec!["()"]);
+    }
 }
diff --git a/src/p23_merge_k_sorted_lists.rs b/src/p23_merge_k_sorted_lists.rs
index 30d0728..c62c420 100644
--- a/src/p23_merge_k_sorted_lists.rs
+++ b/src/p23_merge_k_sorted_lists.rs
@@ -22,21 +22,27 @@ pub mod sorted_vec {
         }
     }
 
-    #[test]
-    fn test1() {
-        assert_eq!(Solution::merge_k_lists(vec![
-            list![1,4,5], list![1,3,4], list![2,6]
-        ]), list![1,1,2,3,4,4,5,6]);
-    }
+    #[cfg(test)]
+    mod tests {
+        use crate::linked_list::ListNode;
+        use super::Solution;
 
-    #[test]
-    fn test2() {
-        assert_eq!(Solution::merge_k_lists(vec![]), list![]);
-    }
+        #[test]
+        fn test1() {
+            assert_eq!(Solution::merge_k_lists(vec![
+                list![1,4,5], list![1,3,4], list![2,6]
+            ]), list![1,1,2,3,4,4,5,6]);
+        }
 
-    #[test]
-    fn test3() {
-        assert_eq!(Solution::merge_k_lists(vec![list![]]), list![]);
+        #[test]
+        fn test2() {
+            assert_eq!(Solution::merge_k_lists(vec![]), list![]);
+        }
+
+        #[test]
+        fn test3() {
+            assert_eq!(Solution::merge_k_lists(vec![list![]]), list![]);
+        }
     }
 }
 
@@ -71,20 +77,26 @@ pub mod binary_heap {
         fn cmp(&self, other: &Self) -> Ordering { self.val.cmp(&other.val) }
     }
 
-    #[test]
-    fn test1() {
-        assert_eq!(Solution::merge_k_lists(vec![
-            list![1,4,5], list![1,3,4], list![2,6]
-        ]), list![1,1,2,3,4,4,5,6]);
-    }
+    #[cfg(test)]
+    mod tests {
+        use crate::linked_list::ListNode;
+        use super::Solution;
 
-    #[test]
-    fn test2() {
-        assert_eq!(Solution::merge_k_lists(vec![]), list![]);
-    }
+        #[test]
+        fn test1() {
+            assert_eq!(Solution::merge_k_lists(vec![
+                list![1,4,5], list![1,3,4], list![2,6]
+            ]), list![1,1,2,3,4,4,5,6]);
+        }
 
-    #[test]
-    fn test3() {
-        assert_eq!(Solution::merge_k_lists(vec![list![]]), list![]);
+        #[test]
+        fn test2() {
+            assert_eq!(Solution::merge_k_lists(vec![]), list![]);
+        }
+
+        #[test]
+        fn test3() {
+            assert_eq!(Solution::merge_k_lists(vec![list![]]), list![]);
+        }
     }
 }
diff --git a/src/p24_swap_nodes_in_pairs.rs b/src/p24_swap_nodes_in_pairs.rs
index 2cdc6b3..56811fa 100644
--- a/src/p24_swap_nodes_in_pairs.rs
+++ b/src/p24_swap_nodes_in_pairs.rs
@@ -18,17 +18,23 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::swap_pairs(list![1,2,3,4]), list![2,1,4,3]);
-}
+#[cfg(test)]
+mod tests {
+    use crate::linked_list::ListNode;
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::swap_pairs(list![]), list![]);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::swap_pairs(list![1,2,3,4]), list![2,1,4,3]);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::swap_pairs(list![1]), list![1]);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::swap_pairs(list![]), list![]);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::swap_pairs(list![1]), list![1]);
+    }
 }
diff --git a/src/p25_reverse_nodes_in_k_group.rs b/src/p25_reverse_nodes_in_k_group.rs
new file mode 100644
index 0000000..b3b9aa3
--- /dev/null
+++ b/src/p25_reverse_nodes_in_k_group.rs
@@ -0,0 +1,24 @@
+use crate::linked_list::ListNode;
+
+pub struct Solution;
+impl Solution {
+    pub fn reverse_k_group(mut head: Option<Box<ListNode>>, k: i32) -> Option<Box<ListNode>> {
+        unimplemented!()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::linked_list::ListNode;
+    use super::Solution;
+
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::reverse_k_group(list![1,2,3,4,5], 2), list![2,1,4,3,5]);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::reverse_k_group(list![1,2,3,4,5], 3), list![3,2,1,4,5]);
+    }
+}
diff --git a/src/p2_add_two_numbers.rs b/src/p2_add_two_numbers.rs
index ce656d7..7578b2c 100644
--- a/src/p2_add_two_numbers.rs
+++ b/src/p2_add_two_numbers.rs
@@ -29,17 +29,24 @@ impl Solution {
     }    
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::add_two_numbers(list![2,4,3], list![5,6,4]), list![7,0,8]);
+#[cfg(test)]
+mod tests {
+    use crate::linked_list::ListNode;
+    use super::Solution;
+
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::add_two_numbers(list![2,4,3], list![5,6,4]), list![7,0,8]);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::add_two_numbers(list![0], list![0]), list![0]);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::add_two_numbers(list![9,9,9,9,9,9,9], list![9,9,9,9]), list![8,9,9,9,0,0,0,1]);
+    }
 }
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::add_two_numbers(list![0], list![0]), list![0]);
-}
-
-#[test]
-fn test3() {
-    assert_eq!(Solution::add_two_numbers(list![9,9,9,9,9,9,9], list![9,9,9,9]), list![8,9,9,9,0,0,0,1]);
-}
diff --git a/src/p3_longest_substring_without_repeating_characters.rs b/src/p3_longest_substring_without_repeating_characters.rs
index 3c48887..73e9f46 100644
--- a/src/p3_longest_substring_without_repeating_characters.rs
+++ b/src/p3_longest_substring_without_repeating_characters.rs
@@ -18,17 +18,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::length_of_longest_substring("abcabcbb".to_string()), 3);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::length_of_longest_substring("bbbbb".to_string()), 1);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::length_of_longest_substring("abcabcbb".to_string()), 3);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::length_of_longest_substring("pwwkew".to_string()), 3);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::length_of_longest_substring("bbbbb".to_string()), 1);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::length_of_longest_substring("pwwkew".to_string()), 3);
+    }
 }
diff --git a/src/p4_median_of_two_sorted_arrays.rs b/src/p4_median_of_two_sorted_arrays.rs
index 4a7189f..c097cbe 100644
--- a/src/p4_median_of_two_sorted_arrays.rs
+++ b/src/p4_median_of_two_sorted_arrays.rs
@@ -20,12 +20,17 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::find_median_sorted_arrays(vec![1,3], vec![2]), 2.0);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::find_median_sorted_arrays(vec![1,2], vec![3,4]), 2.5);
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::find_median_sorted_arrays(vec![1,3], vec![2]), 2.0);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::find_median_sorted_arrays(vec![1,2], vec![3,4]), 2.5);
+    }
 }
diff --git a/src/p5_longest_palindrome_substring.rs b/src/p5_longest_palindrome_substring.rs
index e170242..0f48dd3 100644
--- a/src/p5_longest_palindrome_substring.rs
+++ b/src/p5_longest_palindrome_substring.rs
@@ -15,13 +15,18 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    let actual = Solution::longest_palindrome("babad".to_string());
-    assert!(actual == "bab" || actual == "aba");
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::longest_palindrome("cbbd".to_string()), "bb");
+    #[test]
+    fn test1() {
+        let actual = Solution::longest_palindrome("babad".to_string());
+        assert!(actual == "bab" || actual == "aba");
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::longest_palindrome("cbbd".to_string()), "bb");
+    }
 }
diff --git a/src/p6_zigzag_conversion.rs b/src/p6_zigzag_conversion.rs
index f45bbbf..f178752 100644
--- a/src/p6_zigzag_conversion.rs
+++ b/src/p6_zigzag_conversion.rs
@@ -18,17 +18,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 3), "PAHNAPLSIIGYIR");
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 4), "PINALSIGYAHRPI");
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 3), "PAHNAPLSIIGYIR");
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::convert("A".to_string(), 1), "A");
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 4), "PINALSIGYAHRPI");
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::convert("A".to_string(), 1), "A");
+    }
 }
diff --git a/src/p7_reverse_integer.rs b/src/p7_reverse_integer.rs
index e4d752b..1acf6a2 100644
--- a/src/p7_reverse_integer.rs
+++ b/src/p7_reverse_integer.rs
@@ -17,17 +17,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::reverse(123), 321);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::reverse(-123), -321);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::reverse(123), 321);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::reverse(120), 21);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::reverse(-123), -321);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::reverse(120), 21);
+    }
 }
diff --git a/src/p8_string_to_integer.rs b/src/p8_string_to_integer.rs
index 9b0f433..e4138bc 100644
--- a/src/p8_string_to_integer.rs
+++ b/src/p8_string_to_integer.rs
@@ -19,17 +19,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::my_atoi("42".to_string()), 42);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::my_atoi("   -42".to_string()), -42);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::my_atoi("42".to_string()), 42);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::my_atoi("4193 with words".to_string()), 4193);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::my_atoi("   -42".to_string()), -42);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::my_atoi("4193 with words".to_string()), 4193);
+    }
 }
diff --git a/src/p9_palindrome_number.rs b/src/p9_palindrome_number.rs
index b95e9ca..14b954b 100644
--- a/src/p9_palindrome_number.rs
+++ b/src/p9_palindrome_number.rs
@@ -12,17 +12,22 @@ impl Solution {
     }
 }
 
-#[test]
-fn test1() {
-    assert_eq!(Solution::is_palindrome(121), true);
-}
+#[cfg(test)]
+mod tests {
+    use super::Solution;
 
-#[test]
-fn test2() {
-    assert_eq!(Solution::is_palindrome(-121), false);
-}
+    #[test]
+    fn test1() {
+        assert_eq!(Solution::is_palindrome(121), true);
+    }
 
-#[test]
-fn test3() {
-    assert_eq!(Solution::is_palindrome(10), false);
+    #[test]
+    fn test2() {
+        assert_eq!(Solution::is_palindrome(-121), false);
+    }
+
+    #[test]
+    fn test3() {
+        assert_eq!(Solution::is_palindrome(10), false);
+    }
 }