chore: add nodejs 14 to travis CI matrix and fix functional test fail…

…ure (#2051)

.travis.yml

@@ -7,27 +7,33 @@ os:
 node_js:
 - '10'
 - '12'
+- '14'
 
 # Skip node_js 6 on travis windows workers (as it often fails because
 # travis fails to init the node_js 6 environment).
 jobs:
   fast_finish: true
 
   exclude:
+  # The travis CI windows worker are slower than the linux ones, restrict the
+  # jobs running on windows to just the last nodejs version listed in the.
+  # node_js property.
   - node_js: '10'
     os: windows
+  - node_js: '12'
+    os: windows
 
   include:
   - stage: npm audit and lint github PR title
     ## Keep this in sync with the last version listed in the node_js property.
-    node_js: '12'
+    node_js: '14'
     os: linux
     script:
     - npm run audit-deps
     - npm run travis-pr-title-lint
   - stage: deploy on npm
     ## Keep this in sync with the last version listed in the node_js property.
-    node_js: '12'
+    node_js: '14'
     os: linux
     script: echo "Deploying to npm..."
     ## Make sure we have a production build.

tests/functional/test.cli.run.js

@@ -19,7 +19,7 @@ describe('web-ext run', () => {
        {addonPath: minimalAddonPath},
        (srcDir) => {
          const watchedFile = path.join(srcDir, 'watchedFile.txt');
-         fs.writeFileSync(watchedFile);
+         fs.writeFileSync(watchedFile, '');
 
          const argv = [
            'run', '--verbose', '--no-reload',