Add module with unit tests

Tests.hs

+import Test.HUnit
+
+import Bench (seq, g13, g124, g1245)
+
+test1 = TestCase (assertEqual "g13 11" "{size,10}" (Bench.seq g13 11))
+test2 = TestCase (assertEqual "g124 157" "{size,133}" (Bench.seq g124 157))
+test3 = TestCase (assertEqual "g1245 157" "{size,134}" (Bench.seq g1245 157))
+
+tests = TestList [ TestLabel "seq short" test1
+                 , TestLabel "seq medium" test2
+                 , TestLabel "seq long" test3
+                 ]