Add tests for box-sizing mixin

Closes #60

test/css3/boxSizingSpec.js

@@ -0,0 +1,37 @@
+var render = require('../helper/render');
+var ruleset = require('../helper/ruleset');
+
+describe("CSS3 Boz Sizing", function () {
+
+  describe("CSS3 an argument", function () {
+
+    it("should generate a box-size property", function (done) {
+      render(ruleset('$experimental-support-for-mozilla: false  !global; $experimental-support-for-opera: false  !global; @include box-sizing(border-box)'), function(output, err) {
+        expect(output).toBe(ruleset('-webkit-box-sizing:border-box;box-sizing:border-box'));
+        done();
+      }, ['compass/css3/box-sizing']);
+    });
+
+  });
+
+  describe("CSS3 an empty argument", function () {
+    describe("in a ruleset without other properties", function () {
+      it("should generate nothing", function (done) {
+        render(ruleset('$experimental-support-for-mozilla: false  !global; $experimental-support-for-opera: false  !global; @include box-sizing("")'), function(output, err) {
+          expect(output).toBe('');
+          done();
+        }, ['compass/css3/box-sizing']);
+      });
+    });
+
+    describe("in a ruleset with other properties", function () {
+      it("should generate the other properties", function (done) {
+        render(ruleset('$experimental-support-for-mozilla: false  !global; $experimental-support-for-opera: false  !global; foo: bar; @include box-sizing("")'), function(output, err) {
+          expect(output).toBe(ruleset('foo:bar'));
+          done();
+        }, ['compass/css3/box-sizing']);
+      });
+    });
+  });
+
+});