Align review app with tests

Try to be consistent with the approach taken in the tests by checking for the presence of the `CI` or `HEROKU_APP` environment variables.

This ensures that we only enable certain optimisations when we know we’re running against an up-to-date build (on CI or when deployed to Heroku).

Co-authored-by: Colin Rotherham <colin.rotherham@digital.cabinet-office.gov.uk>

packages/govuk-frontend-review/src/app.mjs

@@ -48,8 +48,7 @@ export default async () => {
 
   // Feature flags
   const flags = /** @type {FeatureFlags} */ ({
-    isDeployedToHeroku: !!process.env.HEROKU_APP,
-    isDevelopment: !['test', 'production'].includes(process.env.NODE_ENV),
+    isDevelopment: !process.env.HEROKU_APP && !process.env.CI,
 
     // Check for JSDoc, SassDoc and Rollup stats
     hasDocsScripts: await hasPath(join(paths.app, 'dist/docs/jsdoc')),
@@ -221,7 +220,7 @@ export default async () => {
         env,
 
         // Skip Nunjucks render from cache in development
-        fixture: !flags.isDevelopment ? fixture : undefined
+        fixture: flags.isDevelopment ? undefined : fixture
       })
 
       let bodyClasses = 'app-template__body'
@@ -278,8 +277,7 @@ export default async () => {
 
 /**
  * @typedef {object} FeatureFlags
- * @property {boolean} isDeployedToHeroku - Review app using `HEROKU_APP`
- * @property {boolean} isDevelopment - Review app not using `NODE_ENV` production or test
+ * @property {boolean} isDevelopment - Review app not in CI or on Heroku
  * @property {boolean} hasDocsStyles - Stylesheets documentation (SassDoc) is available
  * @property {boolean} hasDocsScripts - JavaScripts documentation (JSDoc) is available
  * @property {boolean} hasStats - Rollup stats are available

packages/govuk-frontend-review/src/common/middleware/docs.mjs

@@ -16,10 +16,10 @@ router.get('/', (req, res) => {
  * Sass docs latest release (when deployed)
  */
 router.use('/sass', ({ app }, res, next) => {
-  const { isDeployedToHeroku } =
+  const { isDevelopment } =
     /** @type {import('../../app.mjs').FeatureFlags} */ (app.get('flags'))
 
-  if (isDeployedToHeroku) {
+  if (!isDevelopment) {
     return res.redirect(
       'https://frontend.design-system.service.gov.uk/sass-api-reference/'
     )

packages/govuk-frontend-review/src/common/nunjucks/index.mjs

@@ -22,7 +22,7 @@ export function renderer(app) {
     {
       dev: true, // log stack traces
       express: app, // the Express.js review app that nunjucks should install to
-      noCache: !flags.isDeployedToHeroku, // use cache when deployed only
+      noCache: flags.isDevelopment, // use cache in development only
       watch: flags.isDevelopment // reload templates in development only
     },
     {