Fix test initialization

If multiple specs were to populate the events var, one spec would 
pollute the others. So, let's reset the events var at the beginning of 
each spec.

Co-Authored-By: Antonio Scandurra <as-cii@github.com>

spec/project-spec.js

@@ -1042,11 +1042,12 @@ describe('Project', () => {
   });
 
   describe('.onDidChangeFiles()', () => {
-    let sub = [];
-    const events = [];
+    let sub;
+    let events;
     let checkCallback = () => {};
 
     beforeEach(() => {
+      events = []
       sub = atom.project.onDidChangeFiles(incoming => {
         events.push(...incoming);
         checkCallback();