Added some tests for Math module. Some refactoring in math.c; numeric...

Added some tests for Math module. Some refactoring in math.c; numeric tolerance exported as Math::TOLERANCE and also used for fuzzy tests in mrbtest suite

test/t/math.rb

 ##
 # Math Test
 
+##
+# Performs fuzzy check for equality on methods returning floats
+# on the basis of the Math::TOLERANCE constant.
 def check(a,b)
   a = a.to_f
   b = b.to_f
@@ -11,9 +14,8 @@ def check(a,b)
   end
 end
 
-
 assert('Math.sin 0') do
-  check(Math.sin(0), 1)
+  check(Math.sin(0), 0)
 end
 
 assert('Math.sin PI/2') do
@@ -26,11 +28,12 @@ assert('Fundamental trig identities') do
   N = 15
   N.times do |i|
     a  = Math::PI / N * i
+    ca = Math::PI / 2 - a
     s  = Math.sin(a)
     c  = Math.cos(a)
     t  = Math.tan(a)
-    result &= check(s, Math.cos(Math::PI / 2 - a))
-    result &= check(t, 1 / Math.tan(Math::PI / 2 - a))
+    result &= check(s, Math.cos(ca))
+    result &= check(t, 1 / Math.tan(ca))
     result &= check(s ** 2 + c ** 2, 1)
     result &= check(t ** 2 + 1, (1/c) ** 2)
     result &= check((1/t) ** 2 + 1, (1/s) ** 2)
@@ -100,3 +103,16 @@ assert('Math.hypot') do
   check(Math.hypot(3, 4), 5.0)
 end
 
+assert('Math.frexp 1234') do
+  n = 1234
+  fraction, exponent = Math.frexp(n)
+  check(Math.ldexp(fraction, exponent), n)
+end
+
+assert('Math.erf 1') do
+  check(Math.erf(1), 0.842700792949715)
+end
+
+assert('Math.erfc 1') do
+  check(Math.erfc(1), 0.157299207050285)
+end