Avoid running tests on l10n singleton

We want tests to be independent, so we cannot have them modify a shared
state, such as the l10n singleton. Make sure each test instantiates its
own object instead.

tests/test.localization.js

@@ -1,9 +1,20 @@
 const expect = chai.expect;
-import { l10n } from '../app/localization.js';
+import _, { Localizer, l10n } from '../app/localization.js';
 
 describe('Localization', function () {
     "use strict";
 
+    describe('Singleton', function () {
+        it('should export a singleton object', function () {
+            expect(l10n).to.be.instanceOf(Localizer);
+        });
+        it('should export a singleton translation function', function () {
+            // FIXME: Can we use some spy instead?
+            l10n.dictionary = { "Foobar": "gazonk" };
+            expect(_("Foobar")).to.equal("gazonk");
+        });
+    });
+
     describe('language selection', function () {
         let origNavigator;
         beforeEach(function () {
@@ -20,52 +31,62 @@ describe('Localization', function () {
         });
 
         it('should use English by default', function () {
-            expect(l10n.language).to.equal('en');
+            let lclz = new Localizer();
+            expect(lclz.language).to.equal('en');
         });
         it('should use English if no user language matches', function () {
             window.navigator.languages = ["nl", "de"];
-            l10n.setup(["es", "fr"]);
-            expect(l10n.language).to.equal('en');
+            let lclz = new Localizer();
+            lclz.setup(["es", "fr"]);
+            expect(lclz.language).to.equal('en');
         });
         it('should fall back to generic English for other English', function () {
             window.navigator.languages = ["en-AU", "de"];
-            l10n.setup(["de", "fr", "en-GB"]);
-            expect(l10n.language).to.equal('en');
+            let lclz = new Localizer();
+            lclz.setup(["de", "fr", "en-GB"]);
+            expect(lclz.language).to.equal('en');
         });
         it('should prefer specific English over generic', function () {
             window.navigator.languages = ["en-GB", "de"];
-            l10n.setup(["de", "en-AU", "en-GB"]);
-            expect(l10n.language).to.equal('en-GB');
+            let lclz = new Localizer();
+            lclz.setup(["de", "en-AU", "en-GB"]);
+            expect(lclz.language).to.equal('en-GB');
         });
         it('should use the most preferred user language', function () {
             window.navigator.languages = ["nl", "de", "fr"];
-            l10n.setup(["es", "fr", "de"]);
-            expect(l10n.language).to.equal('de');
+            let lclz = new Localizer();
+            lclz.setup(["es", "fr", "de"]);
+            expect(lclz.language).to.equal('de');
         });
         it('should prefer sub-languages languages', function () {
             window.navigator.languages = ["pt-BR"];
-            l10n.setup(["pt", "pt-BR"]);
-            expect(l10n.language).to.equal('pt-BR');
+            let lclz = new Localizer();
+            lclz.setup(["pt", "pt-BR"]);
+            expect(lclz.language).to.equal('pt-BR');
         });
         it('should fall back to language "parents"', function () {
             window.navigator.languages = ["pt-BR"];
-            l10n.setup(["fr", "pt", "de"]);
-            expect(l10n.language).to.equal('pt');
+            let lclz = new Localizer();
+            lclz.setup(["fr", "pt", "de"]);
+            expect(lclz.language).to.equal('pt');
         });
         it('should not use specific language when user asks for a generic language', function () {
             window.navigator.languages = ["pt", "de"];
-            l10n.setup(["fr", "pt-BR", "de"]);
-            expect(l10n.language).to.equal('de');
+            let lclz = new Localizer();
+            lclz.setup(["fr", "pt-BR", "de"]);
+            expect(lclz.language).to.equal('de');
         });
         it('should handle underscore as a separator', function () {
             window.navigator.languages = ["pt-BR"];
-            l10n.setup(["pt_BR"]);
-            expect(l10n.language).to.equal('pt_BR');
+            let lclz = new Localizer();
+            lclz.setup(["pt_BR"]);
+            expect(lclz.language).to.equal('pt_BR');
         });
         it('should handle difference in case', function () {
             window.navigator.languages = ["pt-br"];
-            l10n.setup(["pt-BR"]);
-            expect(l10n.language).to.equal('pt-BR');
+            let lclz = new Localizer();
+            lclz.setup(["pt-BR"]);
+            expect(lclz.language).to.equal('pt-BR');
         });
     });
 });