diff --git a/leap/src/lib.rs b/leap/src/lib.rs
index fb1ecbc..59ed187 100644
--- a/leap/src/lib.rs
+++ b/leap/src/lib.rs
@@ -1,3 +1,3 @@
 pub fn is_leap_year(year: u64) -> bool {
-    unimplemented!("true if {} is a leap year", year)
+    (year % 4 == 0 && year % 100 != 0) || year % 400 == 0
 }
diff --git a/leap/tests/leap.rs b/leap/tests/leap.rs
index a8a69a4..15451ac 100644
--- a/leap/tests/leap.rs
+++ b/leap/tests/leap.rs
@@ -8,61 +8,51 @@ fn test_year_not_divisible_by_4_common_year() {
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_2_not_divisible_by_4_in_common_year() {
     process_leapyear_case(1970, false);
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_4_not_divisible_by_100_leap_year() {
     process_leapyear_case(1996, true);
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_4_and_5_is_still_a_leap_year() {
     process_leapyear_case(1960, true);
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_100_not_divisible_by_400_common_year() {
     process_leapyear_case(2100, false);
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_100_but_not_by_3_is_still_not_a_leap_year() {
     process_leapyear_case(1900, false);
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_400_leap_year() {
     process_leapyear_case(2000, true);
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_400_but_not_by_125_is_still_a_leap_year() {
     process_leapyear_case(2400, true);
 }
 
 #[test]
-#[ignore]
 fn test_year_divisible_by_200_not_divisible_by_400_common_year() {
     process_leapyear_case(1800, false);
 }
 
 #[test]
-#[ignore]
 fn test_any_old_year() {
     process_leapyear_case(1997, false);
 }
 
 #[test]
-#[ignore]
 fn test_early_years() {
     process_leapyear_case(1, false);
     process_leapyear_case(4, true);
@@ -72,7 +62,6 @@ fn test_early_years() {
 }
 
 #[test]
-#[ignore]
 fn test_century() {
     process_leapyear_case(1700, false);
     process_leapyear_case(1800, false);
@@ -80,7 +69,6 @@ fn test_century() {
 }
 
 #[test]
-#[ignore]
 fn test_exceptional_centuries() {
     process_leapyear_case(1600, true);
     process_leapyear_case(2000, true);
@@ -88,7 +76,6 @@ fn test_exceptional_centuries() {
 }
 
 #[test]
-#[ignore]
 fn test_years_1600_to_1699() {
     let incorrect_years = (1600..1700)
         .filter(|&year| leap::is_leap_year(year) != (year % 4 == 0))