Unit test settings controllers pt 1 (#8155)

* test FontSizeController

Signed-off-by: Kerry Archibald <kerrya@element.io>

* test IncompatibleController

Signed-off-by: Kerry Archibald <kerrya@element.io>

* test SystemFontController

* test ThemeController

Signed-off-by: Kerry Archibald <kerrya@element.io>

* test UseSystemFontController

Signed-off-by: Kerry Archibald <kerrya@element.io>

* fix themecontroller

Signed-off-by: Kerry Archibald <kerrya@element.io>

test/settings/controllers/ThemeController-test.ts

@@ -0,0 +1,75 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import ThemeController from "../../../src/settings/controllers/ThemeController";
+import { SettingLevel } from "../../../src/settings/SettingLevel";
+import SettingsStore from "../../../src/settings/SettingsStore";
+import { DEFAULT_THEME } from "../../../src/theme";
+
+describe('ThemeController', () => {
+    jest.spyOn(SettingsStore, 'getValue').mockReturnValue([]);
+
+    afterEach(() => {
+        // reset
+        ThemeController.isLogin = false;
+    });
+
+    it('returns null when calculatedValue is falsy', () => {
+        const controller = new ThemeController();
+
+        expect(controller.getValueOverride(
+            SettingLevel.ACCOUNT,
+            '$room:server',
+            undefined, /* calculatedValue */
+            SettingLevel.ACCOUNT,
+        )).toEqual(null);
+    });
+
+    it('returns light when login flag is set', () => {
+        const controller = new ThemeController();
+
+        ThemeController.isLogin = true;
+
+        expect(controller.getValueOverride(
+            SettingLevel.ACCOUNT,
+            '$room:server',
+            'dark',
+            SettingLevel.ACCOUNT,
+        )).toEqual('light');
+    });
+
+    it('returns default theme when value is not a valid theme', () => {
+        const controller = new ThemeController();
+
+        expect(controller.getValueOverride(
+            SettingLevel.ACCOUNT,
+            '$room:server',
+            'my-test-theme',
+            SettingLevel.ACCOUNT,
+        )).toEqual(DEFAULT_THEME);
+    });
+
+    it('returns null when value is a valid theme', () => {
+        const controller = new ThemeController();
+
+        expect(controller.getValueOverride(
+            SettingLevel.ACCOUNT,
+            '$room:server',
+            'dark',
+            SettingLevel.ACCOUNT,
+        )).toEqual(null);
+    });
+});