Adding custom pretty print function test.

test/custom-pretty-print-test.js

@@ -0,0 +1,39 @@
+/*
+ * custom-pretty-print-test.js: Test function as pretty print option.
+ *
+ * (C) 2015 Alberto Pose
+ * MIT LICENSE
+ *
+ */
+
+var assert = require('assert'),
+    vows = require('vows'),
+    winston = require('../lib/winston');
+
+/* Custom logging function */
+function myPrettyPrint(obj) {
+  return JSON.stringify(obj)
+    .replace(/\{/g, '< wow ')
+    .replace(/\:/g, ' such ')
+    .replace(/\}/g, ' >');
+}
+
+vows.describe('winston/transport/prettyPrint').addBatch({
+  "When pretty option is used": {
+    "with memory transport": {
+      topic: function () {
+        var transport = new (winston.transports.Memory)({prettyPrint: myPrettyPrint});
+        return this.callback(null, transport);
+      },
+      "should log using a function value": function (_, transport) {
+        transport.log('info', 'hello', {foo: 'bar'}, function (_, logged) {
+          assert.ok(logged);
+          assert.equal(1, transport.writeOutput.length);
+
+          var msg = transport.writeOutput[0];
+          assert.equal('info: hello < wow "foo" such "bar" >', msg);
+        });
+      }
+    }
+  }
+}).export(module);