node tests: Actually test `translations.js`.

Before this test, we were validating the behavior
of `i18next`, but we weren't validating our light
layer that sits on top of `i18next`, which currently
resides in the slightly misnamed `translations.js`
file.

The translations module is now so small that I'll
just quote it verbatim here:

    import i18next from 'i18next';

    i18next.init({
        lng: 'lang',
        resources: {
            lang: {
                translation: page_params.translation_data,
            },
        },
        nsSeparator: false,
        keySeparator: false,
        interpolation: {
            prefix: "__",
            suffix: "__",
        },
        returnEmptyString: false,  // Empty string is not a valid translation.
    });

    window.i18n = i18next;

We now just do `zrequire('translations')` to initialize
the `i18next` library, which allows us to have simpler
test setup and to actually exercise the above call to
`i18next.init`.

This change now gives us 100% line coverage of `translations.js`,
which of course isn't that hard to acheive (see above).

frontend_tests/node_tests/i18n.js

@@ -1,30 +1,23 @@
 set_global('Handlebars', global.make_handlebars());
 zrequire('templates');
 
-// All of our other tests stub out i18n activity;
+// We download our translations in `page_params` (which
-// here we do a quick sanity check on the engine itself.
+// are for the user's chosen language), so we simulate
-const i18next = zrequire('i18next', 'i18next');
+// that here for the tests.
-
+set_global('page_params', {
-global.i18n = i18next;
+    translation_data: {
-
-i18next.init({
-    nsSeparator: false,
-    keySeparator: false,
-    interpolation: {
-        prefix: "__",
-        suffix: "__",
-    },
-    lng: 'fr',
-    resources: {
-        fr: {
-            translation: {
         "Quote and reply": "French translation",
         "Desktop notifications are triggered for messages that are offscreen when they arrive. Mobile and email notifications are triggered once you have been away from Zulip for a few minutes.": "Some French text",
     },
-        },
-    },
 });
 
+// All of our other tests stub out i18n activity;
+// here we do a quick sanity check on the engine itself.
+// We use `translations.js` to initialize `i18next` and
+// to set `i18n` to `i18next` on the global namespace
+// for `templates.js`.
+zrequire('translations');
+
 run_test('t_tag', () => {
     const args = {
         message: {

tools/test-js-with-node

@@ -146,7 +146,6 @@ EXEMPT_FILES = {
     'static/js/todo_widget.js',
     'static/js/topic_list.js',
     'static/js/topic_zoom.js',
-    'static/js/translations.js',
     'static/js/tutorial.js',
     'static/js/typing_events.js',
     'static/js/typing.js',