diff --git a/.gitignore b/.gitignore
index adec40f..f0d11f9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,5 @@ package-lock.json
 build
 package-lock.json
 __pycache__
+.coverage
+.nyc_output
diff --git a/test/test.ts b/test/test.ts
index fe59102..c13c79b 100644
--- a/test/test.ts
+++ b/test/test.ts
@@ -884,7 +884,7 @@ describe('gcs-resumable-upload', () => {
       const scope = nock(REQ_OPTS.url).get(queryPath).reply(200);
       up.getRequestStream(
           REQ_OPTS, (requestStream: stream.Readable&{callback: Function}) => {
-            assert.strictEqual(requestStream.callback.toString(), '() => { }');
+            assert.strictEqual(typeof requestStream.callback, 'function');
             done();
           });
     });