Fix test

src/test/progress-stream-test.js

@@ -17,7 +17,7 @@ describe('progress stream', function () {
         stream.pipeline(input, progress, output, function (error) {
             expect(error).to.not.be.ok();
             const size = fs.statSync(`${__dirname}/progress-stream-test.js`).size;
-            expect(progress._transferred).to.be(size);
+            expect(progress.stats().transferred).to.be(size);
 
             done();
         });