Implementation and testing of this passthrough and adding context as extra argument.

lib/vows.js

@@ -83,16 +83,15 @@ function addVow(vow) {
     });
 
     function runTest(args) {
-        var topic, status;
-
         if (vow.callback instanceof String) {
             return output('pending');
         }
 
         // Run the test, and try to catch `AssertionError`s and other exceptions;
         // increment counters accordingly.
         try {
-            vow.callback.apply(vow.binding || null, args);
+            var env = vow.binding;
+            vow.callback.apply((env && env.binding) || vow.binding || null, args);
             output('honored');
         } catch (e) {
             if (e.name && e.name.match(/AssertionError/)) {

lib/vows/context.js

@@ -1,4 +1,4 @@
-
+var sys = require('sys');
 this.Context = function (vow, ctx, env) {
     var that = this;
 
@@ -9,7 +9,13 @@ this.Context = function (vow, ctx, env) {
     this.env.context = this;
 
     this.env.callback = function (/* arguments */) {
+        var target = this;
         var args = Array.prototype.slice.call(arguments);
+        // Add context as extra argument
+        args.push(that);
+        // Attach a binding to the env...
+        env.binding = target;
+
         var emit = (function (args) {
             //
             // Convert callback-style results into events.

test/vows-test.js

@@ -95,6 +95,25 @@ vows.describe("Vows").addBatch({
             }
         }
     },
+    "a callback-style return": {
+        topic: function() {
+            var target = {a: 1};
+            function f(callback) {
+                callback.call(target, null, 1);
+            }
+            f(this.callback);
+        },
+        'should pass on the user\'s callback arguments': function(err, status) {
+            assert.isNull(err);
+            assert.equal(status, 1);
+        },
+        'should set this to the target of the user\'s callback': function(err, status) {
+            assert.deepEqual(this, {a: 1});
+        },
+        'should pass test context as extra parameter': function(err, status, context) {
+            assert.equal(context.name, "a callback-style return");
+        }
+    },
     "A nested context with no topics": {
         topic: 45,
         ".": {