chore(test): automatically cleanup temp files generated during tests

test/helpers.js

@@ -1,5 +1,6 @@
 const path = require('path')
 const requireAll = require('require-all')
+const tmp = require('tmp')
 
 // require all source code
 // so that the coverage report is accurate
@@ -10,3 +11,7 @@ requireAll(path.join(__dirname, '..', 'src'))
 process.on('unhandledRejection', err => {
   throw err
 })
+
+// Automatically delete temporary files/folders
+// Created during the tests
+tmp.setGracefulCleanup()