Add tests for negative numbers

tests/test_int_comparison.nim

@@ -13,29 +13,44 @@ suite "Signed int - Testing comparison operators":
   let
     a = 10'i16.stint(16)
     b = 15'i16.stint(16)
-    c = 150'u16
+    c = 150'i16.stint(16)
 
   test "< operator":
     check:
       a < b
       not (a + b < b)
       not (a + a + a < b + b)
+      -c < c
+      -c < a
+      -b < -a
+      not(-b < -b)
 
   test "<= operator":
     check:
       a <= b
       not (a + b <= b)
       a + a + a <= b + b
+      -c <= c
+      -c <= a
+      -b <= -a
+      -b <= -b
 
   test "> operator":
     check:
       b > a
       not (b > a + b)
       not (b + b > a + a + a)
+      c > -c
+      a > -c
+      b > -c
+      not(-b > -b)
 
   test ">= operator":
     check:
       b >= a
       not (b >= a + b)
       b + b >= a + a + a
-
+      c >= -c
+      a >= -c
+      b >= -c
+      -b >= -b