diff --git a/test/modules/abs.js b/test/modules/abs.js
index 082c67d..bf88705 100644
--- a/test/modules/abs.js
+++ b/test/modules/abs.js
@@ -4,7 +4,9 @@ if (typeof T === 'undefined') require('../setup');
     T('absoluteValue');
 
     function t(expected, value){
-        T.assertEqual(expected, new Decimal(value).abs().valueOf());
+        var x = new Decimal(value);
+        T.assertEqual(expected, x.abs().valueOf());
+        T.assert(x.eq(value) || x.isNaN());
     }
 
     Decimal.config({
diff --git a/test/modules/cos.js b/test/modules/cos.js
index ce813d2..4d79ac6 100644
--- a/test/modules/cos.js
+++ b/test/modules/cos.js
@@ -6,12 +6,10 @@ if (typeof T === 'undefined') require('../setup');
     function t(n, pr, rm, expected) {
         Decimal.precision = pr;
         Decimal.rounding = rm;
-        T.assertEqual(expected, Decimal.cos(n).valueOf());
-        T.assertEqual(expected, new Decimal(n).cos().valueOf());
-
         var x = new Decimal(n);
-        x.cos();
-        T.assertEqual(new Decimal(n).valueOf(), x.valueOf());
+        T.assertEqual(expected, x.cos().valueOf());
+        T.assertEqual(expected, Decimal.cos(n).valueOf());
+        T.assert(x.eq(n) || x.isNaN());
     }
 
     Decimal.config({
@@ -44,6 +42,7 @@ if (typeof T === 'undefined') require('../setup');
     t('0.3834777777', 3, 4, '0.927');
     t('16355.3334', 9, 4, '0.979658167');
     t('0.997737586545708065463833973312637902054356957830033', 5, 5, '0.5422');
+    t('-0.997737586545708065463833973312637902054356957830033', 5, 5, '0.5422');
     t('7803700', 4, 2, '-0.9032');
     t('841822094288189413002174891207354317', 5, 2, '-0.86017');
     t('67942', 8, 3, '-0.33958641');
diff --git a/test/modules/exp.js b/test/modules/exp.js
index 4dc98be..62d619d 100644
--- a/test/modules/exp.js
+++ b/test/modules/exp.js
@@ -6,8 +6,10 @@ if (typeof T === 'undefined') require('../setup');
     function t(n, expected, pr, rm) {
         Decimal.precision = pr;
         Decimal.rounding = rm;
+        var x = new Decimal(n);
+        T.assertEqual(expected, x.exp().valueOf());
         T.assertEqual(expected, Decimal.exp(n).valueOf());
-        T.assertEqual(expected, new Decimal(n).exp().valueOf());
+        T.assert(x.eq(n) || x.isNaN());
     }
 
     Decimal.config({
diff --git a/test/modules/sin.js b/test/modules/sin.js
index 0eb0299..a5baf1b 100644
--- a/test/modules/sin.js
+++ b/test/modules/sin.js
@@ -6,8 +6,10 @@ if (typeof T === 'undefined') require('../setup');
     function t(n, pr, rm, expected) {
         Decimal.precision = pr;
         Decimal.rounding = rm;
+        var x = new Decimal(n);
+        T.assertEqual(expected, x.sin().valueOf());
         T.assertEqual(expected, Decimal.sin(n).valueOf());
-        T.assertEqual(expected, new Decimal(n).sin().valueOf());
+        T.assert(x.eq(n) || x.isNaN());
     }
 
     Decimal.config({
@@ -28,6 +30,9 @@ if (typeof T === 'undefined') require('../setup');
     t('93332358216', 48, 5, '0.000816283943127306029649893248669685836695194145277');
     t('766737078569022420173292205068953186848344673451240027655054631094318050', 18, 6, '0.00111135055272494455');
 
+    t('-93332358216', 48, 5, '-0.000816283943127306029649893248669685836695194145277');
+    t('-766737078569022420173292205068953186848344673451240027655054631094318050', 18, 6, '-0.00111135055272494455');
+
     t('0.359136383962093189473162700700590970518456985109181875257764726415814563424613193774806585890478208084275468196568294033', 38, 1, '0.35146584650000000000000000000000000006');
     t('3202222222227222222222222222222224222222222222222222222222.222222222222222222222222222', 7, 0, '0.5499568');
     t('8', 5, 6, '0.98936');
diff --git a/test/modules/tan.js b/test/modules/tan.js
index ed12bc9..b6c4902 100644
--- a/test/modules/tan.js
+++ b/test/modules/tan.js
@@ -6,8 +6,10 @@ if (typeof T === 'undefined') require('../setup');
     function t(n, pr, rm, expected) {
         Decimal.precision = pr;
         Decimal.rounding = rm;
+        var x = new Decimal(n);
+        T.assertEqual(expected, x.tan().valueOf());
         T.assertEqual(expected, Decimal.tan(n).valueOf());
-        T.assertEqual(expected, new Decimal(n).tan().valueOf());
+        T.assert(x.eq(n) || x.isNaN());
     }
 
     Decimal.config({
@@ -26,8 +28,10 @@ if (typeof T === 'undefined') require('../setup');
     t('-Infinity', 40, 4, 'NaN');
 
     t('3', 5, 5, '-0.14255');
+    t('-3', 5, 5, '0.14255');
     t('0.8', 7, 6, '1.029639');
     t('539998661123466984649191689138494900416386817996524', 7, 6, '32.04695');
+    t('-539998661123466984649191689138494900416386817996524', 7, 6, '-32.04695');
     t('0.5172293543584894071801901902', 5, 1, '0.56888');
     t('5', 10, 5, '-3.380515006');
     t('0.5283979979897015', 1, 4, '0.6');
diff --git a/test/modules/times.js b/test/modules/times.js
index 260fb83..24e0345 100644
--- a/test/modules/times.js
+++ b/test/modules/times.js
@@ -4,7 +4,9 @@ if (typeof T === 'undefined') require('../setup');
     T('times');
 
     var t = function (multiplicand, multiplier, expected) {
-        T.assertEqual(expected, new Decimal(multiplicand).times(multiplier).valueOf());
+        var x = new Decimal(multiplicand);
+        T.assertEqual(expected, x.times(multiplier).valueOf());
+        T.assert(x.eq(multiplicand) || x.isNaN());
     }
 
     Decimal.config({