Ensure the fp iteratee wrapper enforces arity for functions with a length of 0.

lib/fp/base.js

@@ -102,7 +102,7 @@ function baseConvert(util, name, func) {
         arity = arity > 2 ? (arity - 2) : 1;
         func = iteratee(func);
         var length = func.length;
-        return length <= arity ? func : baseAry(func, arity);
+        return (length && length <= arity) ? func : baseAry(func, arity);
       };
     },
     'mixin': function(mixin) {

test/test-fp.js

@@ -567,6 +567,28 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('reduce methods');
+
+  _.each(['reduce', 'reduceRight'], function(methodName) {
+    var func = fp[methodName],
+        array = [1, 2, 3],
+        isReduce = methodName == 'reduce';
+
+    QUnit.test('`_.' + methodName + '` should provide the correct `iteratee` arguments', function(assert) {
+      assert.expect(1);
+
+      var args;
+
+      func(function() {
+        args || (args = slice.call(arguments));
+      })(0, array);
+
+      assert.deepEqual(args, isReduce ? [0, 1] : [0, 3]);
+    });
+  });
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('fp.runInContext');
 
   (function() {