test cases for stringify

src/util/underscore.js

@@ -11,12 +11,14 @@ function isString (value) {
 }
 
 function stringify (value) {
-  if (!isNil(value)) {
-    if (typeof value.to_liquid === 'function') {
-      return stringify(value.to_liquid())
-    } else if (typeof value.toLiquid === 'function') {
-      return stringify(value.toLiquid())
-    }
+  if (isNil(value)) {
+    return String(value)
+  }
+  if (typeof value.to_liquid === 'function') {
+    return stringify(value.to_liquid())
+  }
+  if (typeof value.toLiquid === 'function') {
+    return stringify(value.toLiquid())
   }
   if (isString(value)) {
     return value

test/util/underscore.js

@@ -44,6 +44,12 @@ describe('util/underscore', function () {
     it('should recursively call toLiquid()', function () {
       expect(_.stringify({toLiquid: () => ({toLiquid: () => 'foo'})})).to.equal('foo')
     })
+    it('should return "null" for null', function () {
+      expect(_.stringify(null)).to.equal('null')
+    })
+    it('should return "undefined" for undefined', function () {
+      expect(_.stringify(undefined)).to.equal('undefined')
+    })
   })
   describe('.forOwn()', function () {
     it('should iterate all properties', function () {