Sync leap tests (#542)

* Sync `leap` tests

* Fix formatting

---------

Co-authored-by: Ryan Hartlage <[email protected]>

Author: BNAndras

exercises/practice/leap/leap_spec.lua

@@ -1,19 +1,39 @@
 local is_leap_year = require('leap')
 
 describe('leap', function()
-  it('a known leap year', function()
+  it('year not divisible by 4 is common year', function()
+    assert.is_false(is_leap_year(2015))
+  end)
+
+  it('year divisible by 2, not divisible by 4 is common year', function()
+    assert.is_false(is_leap_year(1970))
+  end)
+
+  it('year divisible by 4, not divisible by 100 is leap year', function()
     assert.is_true(is_leap_year(1996))
   end)
 
-  it('any old year', function()
-    assert.is_false(is_leap_year(1997))
+  it('year divisible by 4 and 5 is still a leap year', function()
+    assert.is_true(is_leap_year(1960))
+  end)
+
+  it('year divisible by 100, not divisible by 400 is common year', function()
+    assert.is_false(is_leap_year(2100))
   end)
 
-  it('turn of the 20th century', function()
+  it('year divisible by 100 but not by 3 is still not a leap year', function()
     assert.is_false(is_leap_year(1900))
   end)
 
-  it('turn of the 21st century', function()
+  it('year divisible by 400 is leap year', function()
     assert.is_true(is_leap_year(2000))
   end)
+
+  it('year divisible by 400 but not by 125 is still a leap year', function()
+    assert.is_true(is_leap_year(2400))
+  end)
+
+  it('year divisible by 200, not divisible by 400 is common year', function()
+    assert.is_false(is_leap_year(1800))
+  end)
 end)