fix: Install eslint 4.7.1 before running the functional tests on CI

.travis.yml

@@ -11,7 +11,14 @@ before_script:
 
 # Keep this in sync with appveyor.yml
 script:
+## run eslint, flow and the unit test suite.
 - COVERAGE=y NODE_ENV=production npm test
+
+## install the eslint version needed by eslint and run functional test suite
+## (See #1082 for rationale).
+- npm install eslint@4.7.1 && npm test:functional
+
+## lint the github PR title.
 - npm run travis-pr-title-lint
 
 after_script: npm run publish-coverage

Gruntfile.js

@@ -30,13 +30,12 @@ module.exports = function(grunt) {
     'webpack:functional_tests',
   ]);
 
-  grunt.registerTask('test', 'run linting and test suites', function() {
+  grunt.registerTask('test', 'run linting and the unit test suite', function() {
     var tasks = [
       'lint',
       'flowbin:check',
       'build-tests',
       'mochaTest:unit',
-      'mochaTest:functional',
     ];
 
     // TODO: enable the flowbin:check task on AppVeyor (mozilla/web-ext#773)
@@ -48,6 +47,11 @@ module.exports = function(grunt) {
     grunt.task.run(tasks);
   });
 
+  grunt.registerTask('test:functional', 'run functional test suites', [
+    'build-tests',
+    'mochaTest:functional',
+  ]);
+
   grunt.registerTask('develop', [
     'flowbin:start',
     'watch:develop',

appveyor.yml

@@ -21,3 +21,7 @@ test_script:
   - set COVERAGE=y
   - set NODE_ENV=production
   - npm run test
+  ## install the eslint version needed by eslint and run functional test suite
+  ## (See #1082 for rationale).
+  - npm install eslint@4.7.1
+  - npm test:functional

package.json

@@ -17,6 +17,7 @@
     "flow-check": "grunt flowbin:check",
     "lint": "grunt lint",
     "test": "grunt test",
+    "test:functional": "grunt test:functional",
     "publish-coverage": "grunt coveralls",
     "nsp-check": "nsp check -o summary",
     "changelog": "conventional-changelog -p angular -u",