test: Add tests for main package

- Changed jest to run from the root package and reference the packages
  as projects. This required moving the base jest config file away from
  the project root.
- Module isolation seems to prevent ts-jest from loading the shared
  package, so we disabled it for now.
- To better facilitate mocking, services should be split into interfaces
  and implementation
- Had to downgrade to chald 4.1.2 as per
  https://github.com/chalk/chalk/releases/tag/v5.0.0 at least until
  https://github.com/microsoft/TypeScript/issues/46452 is resolved.

35 files changed, 529 insertions, 215 deletions

diff --git a/.gitignore b/.gitignore
index 22394d6..3dfcfec 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@
 !.yarn/plugins
 !.yarn/releases
 !.yarn/versions
+coverage/
 dist/
 node_modules/
 *.tsbuildinfo
diff --git a/config/build-common.js b/config/buildConstants.js
index ff5a218..4952907 100644
--- a/config/build-common.js
+++ b/config/buildConstants.js
@@ -1,6 +1,7 @@
 import { readFileSync } from 'fs';
-import { dirname, join } from 'path';
-import { fileURLToPath } from 'url';
+import { join } from 'path';
+
+import { fileURLToDirname } from './utils.js';
 
 const thisDir = fileURLToDirname(import.meta.url);
 
@@ -37,11 +38,3 @@ export const chrome = `chrome${chromeVersion}`;
 
 /** @type {string} */
 export const node = `node${nodeVersion}`;
-
-/**
- * @param {string} url
- * @returns {string}
- */
-export function fileURLToDirname(url) {
-  return dirname(fileURLToPath(url));
-}
diff --git a/config/esbuild-config.js b/config/esbuildConfig.js
index 5cef85f..05386b1 100644
--- a/config/esbuild-config.js
+++ b/config/esbuildConfig.js
@@ -1,4 +1,4 @@
-import { banner } from './build-common.js';
+import { banner } from './buildConstants.js';
 
 /** @type {string} */
 const mode = process.env.MODE || 'development';
diff --git a/config/jest.config.base.js b/config/jest.config.base.js
new file mode 100644
index 0000000..f265c1c
--- /dev/null
+++ b/config/jest.config.base.js
@@ -0,0 +1,26 @@
+import { join } from 'path';
+
+import { fileURLToDirname } from './utils.js';
+
+const dirname = fileURLToDirname(import.meta.url);
+
+/** @type {import('ts-jest').InitialOptionsTsJest} */
+export default {
+  preset: 'ts-jest/presets/default-esm',
+  globals: {
+    'ts-jest': {
+      useESM: true,
+    },
+  },
+  moduleNameMapper: {
+    '@sophie/(.+)': join(dirname, '../packages/$1/src/index.ts'),
+    '^(\\.{1,2}/.*)\\.js$': '$1',
+  },
+  resetMocks: true,
+  restoreMocks: true,
+  testEnvironment: 'node',
+  testPathIgnorePatterns: [
+    '/dist/',
+    '/node_modules/',
+  ],
+};
diff --git a/config/utils.js b/config/utils.js
new file mode 100644
index 0000000..d3e13d9
--- /dev/null
+++ b/config/utils.js
@@ -0,0 +1,10 @@
+import { dirname } from 'path';
+import { fileURLToPath } from 'url';
+
+/**
+ * @param {string} url
+ * @returns {string}
+ */
+export function fileURLToDirname(url) {
+  return dirname(fileURLToPath(url));
+}
diff --git a/jest.config.js b/jest.config.js
index 1aa0cbb..414e49f 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -1,27 +1,6 @@
-import { join } from 'path';
-
-import { fileURLToDirname } from './config/build-common.js';
-
-const dirname = fileURLToDirname(import.meta.url);
-
 /** @type {import('ts-jest').InitialOptionsTsJest} */
 export default {
-  preset: 'ts-jest/presets/default-esm',
-  globals: {
-    'ts-jest': {
-      isolatedModules: true,
-      useESM: true,
-    },
-  },
-  moduleNameMapper: {
-    '@sophie/(.+)': join(dirname, 'packages/$1/src/index.ts'),
-    '^(\\.{1,2}/.*)\\.js$': '$1',
-  },
-  resetMocks: true,
-  restoreMocks: true,
-  testEnvironment: 'node',
-  testPathIgnorePatterns: [
-    '/dist/',
-    '/node_modules/',
+  projects: [
+    '<rootDir>/packages/*',
   ],
 };
diff --git a/package.json b/package.json
index 22748f7..ab2fc9f 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,7 @@
   "main": "packages/main/dist/index.cjs",
   "scripts": {
     "clean": "rimraf dist packages/*/dist packages/*/tsconfig.tsbuildinfo .vite",
-    "test": "yarn workspaces foreach -vpt run test",
+    "test": "node --experimental-vm-modules node_modules/jest/bin/jest.js",
     "build": "node scripts/build.js",
     "precompile": "cross-env MODE=production yarn run build",
     "compile": "yarn precompile && yarn compile:electron-builder",
@@ -38,7 +38,7 @@
   ],
   "devDependencies": {
     "@electron/fuses": "^1.5.0",
-    "@types/jest": "^27.0.3",
+    "@types/jest": "^27.4.0",
     "@vitejs/plugin-react": "^1.1.3",
     "chokidar": "^3.5.2",
     "cross-env": "^7.0.3",
@@ -51,7 +51,7 @@
     "rollup": "^2.62.0",
     "ts-jest": "^27.1.2",
     "typescript": "^4.5.4",
-    "vite": "^2.7.9"
+    "vite": "^2.7.10"
   },
   "packageManager": "yarn@3.1.1",
   "dependencies": {
diff --git a/packages/main/esbuild.config.js b/packages/main/esbuild.config.js
index a39534d..af52f27 100644
--- a/packages/main/esbuild.config.js
+++ b/packages/main/esbuild.config.js
@@ -1,5 +1,6 @@
-import { node, fileURLToDirname } from '../../config/build-common.js';
-import { getConfig } from '../../config/esbuild-config.js';
+import { node } from '../../config/buildConstants.js';
+import { getConfig } from '../../config/esbuildConfig.js';
+import { fileURLToDirname } from '../../config/utils.js';
 
 const externalPackages = ['electron'];
 
diff --git a/packages/main/jest.config.js b/packages/main/jest.config.js
new file mode 100644
index 0000000..b86463c
--- /dev/null
+++ b/packages/main/jest.config.js
@@ -0,0 +1,3 @@
+import rootConfig from '../../config/jest.config.base.js';
+
+export default rootConfig;
diff --git a/packages/main/package.json b/packages/main/package.json
index 99451bd..eb2ecf6 100644
--- a/packages/main/package.json
+++ b/packages/main/package.json
@@ -10,7 +10,7 @@
   "dependencies": {
     "@sophie/service-shared": "workspace:*",
     "@sophie/shared": "workspace:*",
-    "chalk": "^5.0.0",
+    "chalk": "^4.1.2",
     "electron": "16.0.5",
     "json5": "^2.2.0",
     "lodash-es": "^4.17.21",
@@ -27,6 +27,7 @@
     "@types/node": "^17.0.5",
     "electron-devtools-installer": "^3.2.0",
     "esbuild": "^0.14.9",
+    "jest": "^27.4.5",
     "rimraf": "^3.0.2",
     "typescript": "^4.5.4"
   }
diff --git a/packages/main/src/compositionRoot.ts b/packages/main/src/compositionRoot.ts
index eb6f50f..d420bd6 100644
--- a/packages/main/src/compositionRoot.ts
+++ b/packages/main/src/compositionRoot.ts
@@ -22,12 +22,12 @@ import { app } from 'electron';
 
 import { initConfig } from './controllers/config';
 import { initNativeTheme } from './controllers/nativeTheme';
-import { ConfigPersistenceService } from './services/ConfigPersistenceService';
+import { ConfigPersistenceServiceImpl } from './services/impl/ConfigPersistenceServiceImpl';
 import { MainStore } from './stores/MainStore';
 import { Disposer } from './utils';
 
 export async function init(store: MainStore): Promise<Disposer> {
-  const configPersistenceService = new ConfigPersistenceService(app.getPath('userData'));
+  const configPersistenceService = new ConfigPersistenceServiceImpl(app.getPath('userData'));
   const disposeConfigController = await initConfig(store.config, configPersistenceService);
   const disposeNativeThemeController = initNativeTheme(store);
 
diff --git a/packages/main/src/controllers/__tests__/config.spec.ts b/packages/main/src/controllers/__tests__/config.spec.ts
new file mode 100644
index 0000000..9471ca9
--- /dev/null
+++ b/packages/main/src/controllers/__tests__/config.spec.ts
@@ -0,0 +1,184 @@
+/*
+ * Copyright (C)  2021-2022 Kristóf Marussy <kristof@marussy.com>
+ *
+ * This file is part of Sophie.
+ *
+ * Sophie is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { jest } from '@jest/globals';
+import { mocked } from 'jest-mock';
+import ms from 'ms';
+
+import { initConfig } from '../config';
+import type { ConfigPersistenceService } from '../../services/ConfigPersistenceService';
+import { Config, config as configModel } from '../../stores/Config';
+import { Disposer, silenceLogger } from '../../utils';
+
+let config: Config;
+let persistenceService: ConfigPersistenceService = {
+  readConfig: jest.fn(),
+  writeConfig: jest.fn(),
+  watchConfig: jest.fn(),
+};
+let lessThanThrottleMs = ms('0.1s');
+let throttleMs = ms('1s');
+
+beforeAll(() => {
+  jest.useFakeTimers();
+  silenceLogger();
+});
+
+beforeEach(() => {
+  config = configModel.create();
+});
+
+describe('when initializing', () => {
+  describe('when there is no config file', () => {
+    beforeEach(() => {
+      mocked(persistenceService.readConfig).mockResolvedValueOnce({
+        found: false,
+      });
+    });
+
+    it('should create a new config file', async () => {
+      await initConfig(config, persistenceService);
+      expect(persistenceService.writeConfig).toBeCalledTimes(1);
+    });
+
+    it('should bail if there is an an error creating the config file', async () => {
+      mocked(persistenceService.writeConfig).mockRejectedValue(new Error('boo'));
+      await expect(() => initConfig(config, persistenceService)).rejects.toBeInstanceOf(Error);
+    });
+  });
+
+  describe('when there is a valid config file', () => {
+    beforeEach(() => {
+      mocked(persistenceService.readConfig).mockResolvedValueOnce({
+        found: true,
+        data: {
+          themeSource: 'dark',
+        },
+      });
+    });
+
+    it('should read the existing config file is there is one', async () => {
+      await initConfig(config, persistenceService);
+      expect(persistenceService.writeConfig).not.toBeCalled();
+      expect(config.themeSource).toBe('dark');
+    });
+
+    it('should bail if it cannot set up a watcher', async () => {
+      mocked(persistenceService.watchConfig).mockImplementationOnce(() => {
+        throw new Error('boo');
+      });
+      await expect(() => initConfig(config, persistenceService)).rejects.toBeInstanceOf(Error);
+    });
+  });
+
+  it('should not apply an invalid config file', async () => {
+    mocked(persistenceService.readConfig).mockResolvedValueOnce({
+      found: true,
+      data: {
+        themeSource: -1,
+      },
+    });
+    await initConfig(config, persistenceService);
+    expect(config.themeSource).not.toBe(-1);
+  });
+
+  it('should bail if it cannot determine whether there is a config file', async () => {
+    mocked(persistenceService.readConfig).mockRejectedValue(new Error('boo'));
+    await expect(() => initConfig(config, persistenceService)).rejects.toBeInstanceOf(Error);
+  });
+});
+
+describe('when it has loaded the config', () => {
+  let sutDisposer: Disposer;
+  let watcherDisposer: Disposer = jest.fn();
+  let configChangedCallback: () => Promise<void>;
+
+  beforeEach(async () => {
+    mocked(persistenceService.readConfig).mockResolvedValueOnce({
+      found: true,
+      data: {},
+    });
+    mocked(persistenceService.watchConfig).mockReturnValueOnce(watcherDisposer);
+    sutDisposer = await initConfig(config, persistenceService, throttleMs);
+    configChangedCallback = mocked(persistenceService.watchConfig).mock.calls[0][0];
+    jest.resetAllMocks();
+  });
+
+  it('should throttle saving changes to the config file', () => {
+    mocked(persistenceService.writeConfig).mockResolvedValue(undefined);
+    config.setThemeSource('dark');
+    jest.advanceTimersByTime(lessThanThrottleMs);
+    config.setThemeSource('light');
+    jest.advanceTimersByTime(throttleMs);
+    expect(persistenceService.writeConfig).toBeCalledTimes(1);
+  });
+
+  it('should handle config writing errors gracefully', () => {
+    mocked(persistenceService.writeConfig).mockRejectedValue(new Error('boo'));
+    config.setThemeSource('dark');
+    jest.advanceTimersByTime(throttleMs);
+    expect(persistenceService.writeConfig).toBeCalledTimes(1);
+  });
+
+  it('should read the config file when it has changed', async () => {
+    mocked(persistenceService.readConfig).mockResolvedValueOnce({
+      found: true,
+      data: {
+        themeSource: 'dark',
+      },
+    });
+    await configChangedCallback();
+    // Do not write back the changes we have just read.
+    expect(persistenceService.writeConfig).not.toBeCalled();
+    expect(config.themeSource).toBe('dark');
+  });
+
+  it('should not apply an invalid config file when it has changed', async () => {
+    mocked(persistenceService.readConfig).mockResolvedValueOnce({
+      found: true,
+      data: {
+        themeSource: -1,
+      },
+    });
+    await configChangedCallback();
+    expect(config.themeSource).not.toBe(-1);
+  });
+
+  it('should handle config writing errors gracefully', async () => {
+    mocked(persistenceService.readConfig).mockRejectedValue(new Error('boo'));
+    await configChangedCallback();
+  });
+
+  describe('when it was disposed', () => {
+    beforeEach(() => {
+      sutDisposer();
+    });
+
+    it('should dispose the watcher', () => {
+      expect(watcherDisposer).toBeCalled();
+    });
+
+    it('should not listen to store changes any more', () => {
+      config.setThemeSource('dark');
+      jest.advanceTimersByTime(2 * throttleMs);
+      expect(persistenceService.writeConfig).not.toBeCalled();
+    });
+  });
+});
diff --git a/packages/main/src/controllers/__tests__/nativeTheme.spec.ts b/packages/main/src/controllers/__tests__/nativeTheme.spec.ts
new file mode 100644
index 0000000..cfb557c
--- /dev/null
+++ b/packages/main/src/controllers/__tests__/nativeTheme.spec.ts
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C)  2021-2022 Kristóf Marussy <kristof@marussy.com>
+ *
+ * This file is part of Sophie.
+ *
+ * Sophie is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { jest } from '@jest/globals';
+import { mocked } from 'jest-mock';
+
+import { createMainStore, MainStore } from '../../stores/MainStore';
+import { Disposer } from '../../utils';
+
+let shouldUseDarkColors = false;
+
+jest.unstable_mockModule('electron', () => ({
+  nativeTheme: {
+    themeSource: 'system',
+    get shouldUseDarkColors() {
+      return shouldUseDarkColors;
+    },
+    on: jest.fn(),
+    off: jest.fn(),
+  },
+}));
+
+const { nativeTheme } = await import('electron');
+const { initNativeTheme } = await import('../nativeTheme');
+
+let store: MainStore;
+let disposeSut: Disposer;
+
+beforeEach(() => {
+  store = createMainStore();
+  disposeSut = initNativeTheme(store);
+});
+
+it('should register a nativeTheme updated listener', () => {
+  expect(nativeTheme.on).toBeCalledWith('updated', expect.anything());
+});
+
+it('should synchronize themeSource changes to the nativeTheme', () => {
+  store.config.setThemeSource('dark');
+  expect(nativeTheme.themeSource).toBe('dark');
+});
+
+it('should synchronize shouldUseDarkColors changes to the store', () => {
+  const listener = mocked(nativeTheme.on).mock.calls.find(([event]) => event === 'updated')![1];
+  shouldUseDarkColors = true;
+  listener();
+  expect(store.shared.shouldUseDarkColors).toBe(true);
+});
+
+it('should remove the listener on dispose', () => {
+  const listener = mocked(nativeTheme.on).mock.calls.find(([event]) => event === 'updated')![1];
+  disposeSut();
+  expect(nativeTheme.off).toBeCalledWith('updated', listener);
+});
diff --git a/packages/main/src/controllers/config.ts b/packages/main/src/controllers/config.ts
index 600a142..d3559c8 100644
--- a/packages/main/src/controllers/config.ts
+++ b/packages/main/src/controllers/config.ts
@@ -60,12 +60,8 @@ export async function initConfig(
 
   if (!await readConfig()) {
     log.info('Config file was not found');
-    try {
-      await writeConfig();
-      log.info('Created config file');
-    } catch (err) {
-      log.error('Failed to initialize config', err);
-    }
+    await writeConfig();
+    log.info('Created config file');
   }
 
   const disposeOnSnapshot = onSnapshot(config, debounce((snapshot) => {
@@ -73,12 +69,16 @@ export async function initConfig(
     if (lastSnapshotOnDisk !== snapshot) {
       writeConfig().catch((err) => {
         log.error('Failed to write config on config change', err);
-      })
+      });
     }
   }, debounceTime));
 
   const disposeWatcher = persistenceService.watchConfig(async () => {
-    await readConfig();
+    try {
+      await readConfig();
+    } catch (err) {
+      log.error('Failed to read config', err);
+    }
   }, debounceTime);
 
   return () => {
diff --git a/packages/main/src/services/ConfigPersistenceService.ts b/packages/main/src/services/ConfigPersistenceService.ts
index b2109f6..b3ad162 100644
--- a/packages/main/src/services/ConfigPersistenceService.ts
+++ b/packages/main/src/services/ConfigPersistenceService.ts
@@ -17,112 +17,16 @@
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
-import { watch } from 'fs';
-import { readFile, stat, writeFile } from 'fs/promises';
-import JSON5 from 'json5';
-import throttle from 'lodash-es/throttle';
-import { join } from 'path';
 
 import type { ConfigSnapshotOut } from  '../stores/Config';
-import { Disposer, getLogger } from '../utils';
-
-const log = getLogger('configPersistence');
+import { Disposer } from '../utils';
 
 export type ReadConfigResult = { found: true; data: unknown; } | { found: false; };
 
-export class ConfigPersistenceService {
-  private readonly configFilePath: string;
-
-  private writingConfig = false;
-
-  private timeLastWritten: Date | null = null;
-
-  constructor(
-    private readonly userDataDir: string,
-    private readonly configFileName: string = 'config.json5',
-  ) {
-    this.configFileName = configFileName;
-    this.configFilePath = join(this.userDataDir, this.configFileName);
-  }
-
-  async readConfig(): Promise<ReadConfigResult> {
-    let configStr;
-    try {
-      configStr = await readFile(this.configFilePath, 'utf8');
-    } catch (err) {
-      if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
-        log.debug('Config file', this.configFilePath, 'was not found');
-        return { found: false };
-      }
-      throw err;
-    }
-    log.info('Read config file', this.configFilePath);
-    return {
-      found: true,
-      data: JSON5.parse(configStr),
-    };
-  }
-
-  async writeConfig(configSnapshot: ConfigSnapshotOut): Promise<void> {
-    const configJson = JSON5.stringify(configSnapshot, {
-      space: 2,
-    });
-    this.writingConfig = true;
-    try {
-      await writeFile(this.configFilePath, configJson, 'utf8');
-      const { mtime } = await stat(this.configFilePath);
-      log.trace('Config file', this.configFilePath, 'last written at', mtime);
-      this.timeLastWritten = mtime;
-    } finally {
-      this.writingConfig = false;
-    }
-    log.info('Wrote config file', this.configFilePath);
-  }
-
-  watchConfig(callback: () => Promise<void>, throttleMs: number): Disposer {
-    log.debug('Installing watcher for', this.userDataDir);
-
-    const configChanged = throttle(async () => {
-      let mtime: Date;
-      try {
-        const stats = await stat(this.configFilePath);
-        mtime = stats.mtime;
-        log.trace('Config file last modified at', mtime);
-      } catch (err) {
-        if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
-          log.debug('Config file', this.configFilePath, 'was deleted after being changed');
-          return;
-        }
-        throw err;
-      }
-      if (!this.writingConfig
-        && (this.timeLastWritten === null || mtime > this.timeLastWritten)) {
-        log.debug(
-          'Found a config file modified at',
-          mtime,
-          'whish is newer than last written',
-          this.timeLastWritten,
-        );
-        return callback();
-      }
-    }, throttleMs);
-
-    const watcher = watch(this.userDataDir, {
-      persistent: false,
-    });
+export interface ConfigPersistenceService {
+  readConfig(): Promise<ReadConfigResult>;
 
-    watcher.on('change', (eventType, filename) => {
-      if (eventType === 'change'
-        && (filename === this.configFileName || filename === null)) {
-        configChanged()?.catch((err) => {
-          console.log('Unhandled error while listening for config changes', err);
-        });
-      }
-    });
+  writeConfig(configSnapshot: ConfigSnapshotOut): Promise<void>;
 
-    return () => {
-      log.trace('Removing watcher for', this.configFilePath);
-      watcher.close();
-    };
-  }
+  watchConfig(callback: () => Promise<void>, throttleMs: number): Disposer;
 }
diff --git a/packages/main/src/services/impl/ConfigPersistenceServiceImpl.ts b/packages/main/src/services/impl/ConfigPersistenceServiceImpl.ts
new file mode 100644
index 0000000..bffc38c
--- /dev/null
+++ b/packages/main/src/services/impl/ConfigPersistenceServiceImpl.ts
@@ -0,0 +1,128 @@
+
+/*
+ * Copyright (C)  2021-2022 Kristóf Marussy <kristof@marussy.com>
+ *
+ * This file is part of Sophie.
+ *
+ * Sophie is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { watch } from 'fs';
+import { readFile, stat, writeFile } from 'fs/promises';
+import JSON5 from 'json5';
+import throttle from 'lodash-es/throttle';
+import { join } from 'path';
+
+import type { ConfigPersistenceService, ReadConfigResult } from '../ConfigPersistenceService';
+import type { ConfigSnapshotOut } from  '../../stores/Config';
+import { Disposer, getLogger } from '../../utils';
+
+const log = getLogger('configPersistence');
+
+export class ConfigPersistenceServiceImpl implements ConfigPersistenceService {
+  private readonly configFilePath: string;
+
+  private writingConfig = false;
+
+  private timeLastWritten: Date | null = null;
+
+  constructor(
+    private readonly userDataDir: string,
+    private readonly configFileName: string = 'config.json5',
+  ) {
+    this.configFileName = configFileName;
+    this.configFilePath = join(this.userDataDir, this.configFileName);
+  }
+
+  async readConfig(): Promise<ReadConfigResult> {
+    let configStr;
+    try {
+      configStr = await readFile(this.configFilePath, 'utf8');
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
+        log.debug('Config file', this.configFilePath, 'was not found');
+        return { found: false };
+      }
+      throw err;
+    }
+    log.info('Read config file', this.configFilePath);
+    return {
+      found: true,
+      data: JSON5.parse(configStr),
+    };
+  }
+
+  async writeConfig(configSnapshot: ConfigSnapshotOut): Promise<void> {
+    const configJson = JSON5.stringify(configSnapshot, {
+      space: 2,
+    });
+    this.writingConfig = true;
+    try {
+      await writeFile(this.configFilePath, configJson, 'utf8');
+      const { mtime } = await stat(this.configFilePath);
+      log.trace('Config file', this.configFilePath, 'last written at', mtime);
+      this.timeLastWritten = mtime;
+    } finally {
+      this.writingConfig = false;
+    }
+    log.info('Wrote config file', this.configFilePath);
+  }
+
+  watchConfig(callback: () => Promise<void>, throttleMs: number): Disposer {
+    log.debug('Installing watcher for', this.userDataDir);
+
+    const configChanged = throttle(async () => {
+      let mtime: Date;
+      try {
+        const stats = await stat(this.configFilePath);
+        mtime = stats.mtime;
+        log.trace('Config file last modified at', mtime);
+      } catch (err) {
+        if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
+          log.debug('Config file', this.configFilePath, 'was deleted after being changed');
+          return;
+        }
+        throw err;
+      }
+      if (!this.writingConfig
+        && (this.timeLastWritten === null || mtime > this.timeLastWritten)) {
+        log.debug(
+          'Found a config file modified at',
+          mtime,
+          'whish is newer than last written',
+          this.timeLastWritten,
+        );
+        return callback();
+      }
+    }, throttleMs);
+
+    const watcher = watch(this.userDataDir, {
+      persistent: false,
+    });
+
+    watcher.on('change', (eventType, filename) => {
+      if (eventType === 'change'
+        && (filename === this.configFileName || filename === null)) {
+        configChanged()?.catch((err) => {
+          console.log('Unhandled error while listening for config changes', err);
+        });
+      }
+    });
+
+    return () => {
+      log.trace('Removing watcher for', this.configFilePath);
+      watcher.close();
+    };
+  }
+}
diff --git a/packages/main/src/utils/index.ts b/packages/main/src/utils/index.ts
index 9a57e02..2b85989 100644
--- a/packages/main/src/utils/index.ts
+++ b/packages/main/src/utils/index.ts
@@ -22,4 +22,4 @@ import { IDisposer } from 'mobx-state-tree';
 
 export type Disposer = IDisposer;
 
-export { getLogger } from './logging';
+export { getLogger, silenceLogger } from './logging';
diff --git a/packages/main/src/utils/logging.ts b/packages/main/src/utils/logging.ts
index 6c4cba2..ed40365 100644
--- a/packages/main/src/utils/logging.ts
+++ b/packages/main/src/utils/logging.ts
@@ -18,17 +18,17 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import chalk, { ChalkInstance } from 'chalk';
+import chalk, { Chalk } from 'chalk';
 import loglevel, { Logger } from 'loglevel';
 import prefix from 'loglevel-plugin-prefix';
 
-if (import.meta.env.DEV) {
+if (import.meta.env?.DEV) {
   loglevel.setLevel('debug');
 } else {
   loglevel.setLevel('info');
 }
 
-const COLORS: Partial<Record<string, ChalkInstance>> = {
+const COLORS: Partial<Record<string, Chalk>> = {
   TRACE: chalk.magenta,
   DEBUG: chalk.cyan,
   INFO: chalk.blue,
@@ -37,7 +37,7 @@ const COLORS: Partial<Record<string, ChalkInstance>> = {
   CRITICAL: chalk.red,
 };
 
-function getColor(level: string): ChalkInstance {
+function getColor(level: string): Chalk {
   return COLORS[level] ?? chalk.gray;
 }
 
@@ -52,3 +52,11 @@ prefix.apply(loglevel, {
 export function getLogger(loggerName: string): Logger {
   return loglevel.getLogger(loggerName);
 }
+
+export function silenceLogger(): void {
+  loglevel.disableAll();
+  const loggers = loglevel.getLoggers();
+  for (const loggerName of Object.keys(loggers)) {
+    loggers[loggerName].disableAll();
+  }
+}
diff --git a/packages/main/tsconfig.json b/packages/main/tsconfig.json
index 10f5765..1401445 100644
--- a/packages/main/tsconfig.json
+++ b/packages/main/tsconfig.json
@@ -3,6 +3,7 @@
   "compilerOptions": {
     "noEmit": true,
     "types": [
+      "@types/jest",
       "node"
     ]
   },
diff --git a/packages/preload/esbuild.config.js b/packages/preload/esbuild.config.js
index de51fc5..b73a071 100644
--- a/packages/preload/esbuild.config.js
+++ b/packages/preload/esbuild.config.js
@@ -1,5 +1,6 @@
-import { chrome, fileURLToDirname } from '../../config/build-common.js';
-import { getConfig } from '../../config/esbuild-config.js';
+import { chrome } from '../../config/buildConstants.js';
+import { getConfig } from '../../config/esbuildConfig.js';
+import { fileURLToDirname } from '../../config/utils.js';
 
 export default getConfig({
   absWorkingDir: fileURLToDirname(import.meta.url),
diff --git a/packages/preload/jest.config.js b/packages/preload/jest.config.js
index faecf9a..e474c4c 100644
--- a/packages/preload/jest.config.js
+++ b/packages/preload/jest.config.js
@@ -1,4 +1,4 @@
-import rootConfig from '../../jest.config.js';
+import rootConfig from '../../config/jest.config.base.js';
 
 /** @type {import('ts-jest').InitialOptionsTsJest} */
 export default {
diff --git a/packages/preload/package.json b/packages/preload/package.json
index e6dd0ee..9818ba8 100644
--- a/packages/preload/package.json
+++ b/packages/preload/package.json
@@ -6,7 +6,6 @@
   "type": "module",
   "types": "dist-types/index.d.ts",
   "scripts": {
-    "test": "node --experimental-vm-modules ../../node_modules/jest/bin/jest.js",
     "typecheck": "tsc"
   },
   "dependencies": {
@@ -16,7 +15,7 @@
     "mobx-state-tree": "^5.1.0"
   },
   "devDependencies": {
-    "@types/jest": "^27.0.3",
+    "@types/jest": "^27.4.0",
     "jest": "^27.4.5",
     "jest-mock": "^27.4.2",
     "jsdom": "^19.0.0",
diff --git a/packages/preload/src/contextBridge/__tests__/SophieRendererImpl.spec.ts b/packages/preload/src/contextBridge/__tests__/SophieRendererImpl.spec.ts
index 41937c2..fdd1cc5 100644
--- a/packages/preload/src/contextBridge/__tests__/SophieRendererImpl.spec.ts
+++ b/packages/preload/src/contextBridge/__tests__/SophieRendererImpl.spec.ts
@@ -18,7 +18,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import { describe, it, jest } from '@jest/globals';
+import { jest } from '@jest/globals';
 import { mocked } from 'jest-mock';
 import log from 'loglevel';
 import type { IJsonPatch } from 'mobx-state-tree';
@@ -67,7 +67,9 @@ const invalidAction = {
   action: 'not-a-valid-action',
 } as unknown as Action;
 
-log.disableAll();
+beforeAll(() => {
+  log.disableAll();
+});
 
 describe('createSophieRenderer', () => {
   it('registers a shared store patch listener', () => {
@@ -95,59 +97,59 @@ describe('SophieRendererImpl', () => {
   });
 
   describe('onSharedStoreChange', () => {
-    it('requests a snapshot from the main process', async () => {
+    it('should request a snapshot from the main process', async () => {
       mocked(ipcRenderer.invoke).mockResolvedValueOnce(snapshot);
       await sut.onSharedStoreChange(listener);
       expect(ipcRenderer.invoke).toBeCalledWith(RendererToMainIpcMessage.GetSharedStoreSnapshot);
       expect(listener.onSnapshot).toBeCalledWith(snapshot);
     });
 
-    it('catches IPC errors without exposing them', async () => {
+    it('should catch IPC errors without exposing them', async () => {
       mocked(ipcRenderer.invoke).mockRejectedValue(new Error('s3cr3t'));
       await expect(sut.onSharedStoreChange(listener)).rejects.not.toHaveProperty(
         'message',
         expect.stringMatching(/s3cr3t/),
       );
-      expect(listener.onSnapshot).toBeCalledTimes(0);
+      expect(listener.onSnapshot).not.toBeCalled();
     });
 
-    it('does not pass on invalid snapshots', async () => {
+    it('should not pass on invalid snapshots', async () => {
       mocked(ipcRenderer.invoke).mockResolvedValueOnce(invalidSnapshot);
       await expect(sut.onSharedStoreChange(listener)).rejects.toBeInstanceOf(Error);
-      expect(listener.onSnapshot).toBeCalledTimes(0);
+      expect(listener.onSnapshot).not.toBeCalled();
     });
   });
 
   describe('dispatchAction', () => {
-    it('dispatched valid actions', () => {
+    it('should dispatch valid actions', () => {
       sut.dispatchAction(action);
       expect(ipcRenderer.send).toBeCalledWith(RendererToMainIpcMessage.DispatchAction, action);
     });
 
-    it('does not dispatch invalid actions', () => {
+    it('should not dispatch invalid actions', () => {
       expect(() => sut.dispatchAction(invalidAction)).toThrowError();
-      expect(ipcRenderer.send).toBeCalledTimes(0);
+      expect(ipcRenderer.send).not.toBeCalled();
     });
   });
 
   describe('when no listener is registered', () => {
-    it('discards the received patch without any error', () => {
+    it('should discard the received patch without any error', () => {
       onSharedStorePatch(event, patch);
     });
   });
 
   function itRefusesToRegisterAnotherListener() {
-    it('refuses to register another listener', async () => {
+    it('should refuse to register another listener', async () => {
       await expect(sut.onSharedStoreChange(listener)).rejects.toBeInstanceOf(Error);
     });
   }
 
   function itDoesNotPassPatchesToTheListener(
-    name: string = 'does not pass patches to the listener',
+    name: string = 'should not pass patches to the listener',
   ) {
     it(name, () => {
       onSharedStorePatch(event, patch);
-      expect(listener.onPatch).toBeCalledTimes(0);
+      expect(listener.onPatch).not.toBeCalled();
     });
   }
 
@@ -157,12 +159,12 @@ describe('SophieRendererImpl', () => {
       await sut.onSharedStoreChange(listener);
     });
 
-    it('passes patches to the listener', () => {
+    it('should pass patches to the listener', () => {
       onSharedStorePatch(event, patch);
       expect(listener.onPatch).toBeCalledWith(patch);
     });
 
-    it('catches listener errors', () => {
+    it('should catch listener errors', () => {
       mocked(listener.onPatch).mockImplementation(() => { throw new Error(); });
       onSharedStorePatch(event, patch);
     });
@@ -176,7 +178,7 @@ describe('SophieRendererImpl', () => {
         listener.onPatch.mockRestore();
       });
 
-      itDoesNotPassPatchesToTheListener('does not pass on patches any more');
+      itDoesNotPassPatchesToTheListener('should not pass on patches any more');
     });
   });
 
diff --git a/packages/preload/tsconfig.json b/packages/preload/tsconfig.json
index 0f27305..741d435 100644
--- a/packages/preload/tsconfig.json
+++ b/packages/preload/tsconfig.json
@@ -6,6 +6,9 @@
       "dom",
       "dom.iterable",
       "esnext"
+    ],
+    "types": [
+      "@types/jest"
     ]
   },
   "references": [
diff --git a/packages/renderer/package.json b/packages/renderer/package.json
index 2a26b2b..0a9f4ef 100644
--- a/packages/renderer/package.json
+++ b/packages/renderer/package.json
@@ -30,6 +30,6 @@
     "remotedev": "^0.2.9",
     "rimraf": "^3.0.2",
     "typescript": "^4.5.4",
-    "vite": "^2.7.9"
+    "vite": "^2.7.10"
   }
 }
diff --git a/packages/renderer/vite.config.js b/packages/renderer/vite.config.js
index 6f3d351..82ce33d 100644
--- a/packages/renderer/vite.config.js
+++ b/packages/renderer/vite.config.js
@@ -4,7 +4,8 @@ import { builtinModules } from 'module';
 import { join } from 'path';
 import react from '@vitejs/plugin-react';
 
-import { banner, chrome, fileURLToDirname } from '../../config/build-common.js';
+import { banner, chrome } from '../../config/buildConstants.js';
+import { fileURLToDirname } from '../../config/utils.js';
 
 const thisDir = fileURLToDirname(import.meta.url);
 
diff --git a/packages/service-inject/esbuild.config.js b/packages/service-inject/esbuild.config.js
index 3f1d6d0..2169c8e 100644
--- a/packages/service-inject/esbuild.config.js
+++ b/packages/service-inject/esbuild.config.js
@@ -1,5 +1,6 @@
-import { chrome, fileURLToDirname } from '../../config/build-common.js';
-import { getConfig } from '../../config/esbuild-config.js';
+import { chrome } from '../../config/buildConstants.js';
+import { getConfig } from '../../config/esbuildConfig.js';
+import { fileURLToDirname } from '../../config/utils.js';
 
 export default getConfig({
   absWorkingDir: fileURLToDirname(import.meta.url),
diff --git a/packages/service-preload/esbuild.config.js b/packages/service-preload/esbuild.config.js
index 3c67b31..b73a071 100644
--- a/packages/service-preload/esbuild.config.js
+++ b/packages/service-preload/esbuild.config.js
@@ -1,5 +1,6 @@
-import { chrome, fileURLToDirname } from "../../config/build-common.js";
-import { getConfig } from '../../config/esbuild-config.js';
+import { chrome } from '../../config/buildConstants.js';
+import { getConfig } from '../../config/esbuildConfig.js';
+import { fileURLToDirname } from '../../config/utils.js';
 
 export default getConfig({
   absWorkingDir: fileURLToDirname(import.meta.url),
diff --git a/packages/service-shared/esbuild.config.js b/packages/service-shared/esbuild.config.js
index 8df2edf..071ca7d 100644
--- a/packages/service-shared/esbuild.config.js
+++ b/packages/service-shared/esbuild.config.js
@@ -1,5 +1,6 @@
-import { chrome, fileURLToDirname } from '../../config/build-common.js';
-import { getConfig } from '../../config/esbuild-config.js';
+import { chrome } from '../../config/buildConstants.js';
+import { getConfig } from '../../config/esbuildConfig.js';
+import { fileURLToDirname } from '../../config/utils.js';
 
 export default getConfig({
   absWorkingDir: fileURLToDirname(import.meta.url),
diff --git a/packages/shared/esbuild.config.js b/packages/shared/esbuild.config.js
index fbaa6f1..b134931 100644
--- a/packages/shared/esbuild.config.js
+++ b/packages/shared/esbuild.config.js
@@ -1,5 +1,6 @@
-import { chrome, fileURLToDirname } from '../../config/build-common.js';
-import { getConfig } from '../../config/esbuild-config.js';
+import { chrome } from '../../config/buildConstants.js';
+import { getConfig } from '../../config/esbuildConfig.js';
+import { fileURLToDirname } from '../../config/utils.js';
 
 export default getConfig({
   absWorkingDir: fileURLToDirname(import.meta.url),
diff --git a/scripts/build.js b/scripts/build.js
index 9b9b26e..ef2b998 100644
--- a/scripts/build.js
+++ b/scripts/build.js
@@ -2,7 +2,7 @@ import { build as esbuildBuild } from 'esbuild';
 import { join } from 'path';
 import { build as viteBuild } from 'vite';
 
-import { fileURLToDirname } from '../config/build-common.js';
+import { fileURLToDirname } from '../config/utils.js';
 
 const thisDir = fileURLToDirname(import.meta.url);
 
diff --git a/scripts/update-electron-vendors.js b/scripts/update-electron-vendors.js
index fea8b9d..b2f4ca4 100644
--- a/scripts/update-electron-vendors.js
+++ b/scripts/update-electron-vendors.js
@@ -3,7 +3,7 @@ import electronPath from 'electron';
 import { writeFile } from 'fs/promises';
 import { join, resolve } from 'path';
 
-import { fileURLToDirname } from '../config/build-common.js';
+import { fileURLToDirname } from '../config/utils.js';
 
 /**
  * Returns versions of electron vendors
diff --git a/scripts/watch.js b/scripts/watch.js
index 82a8feb..b635fac 100644
--- a/scripts/watch.js
+++ b/scripts/watch.js
@@ -5,7 +5,7 @@ import electronPath from 'electron';
 import { join } from 'path';
 import { createServer } from 'vite';
 
-import { fileURLToDirname } from '../config/build-common.js';
+import { fileURLToDirname } from '../config/utils.js';
 
 /** @type {string} */
 const thisDir = fileURLToDirname(import.meta.url);
@@ -127,7 +127,7 @@ function setupMainPackageWatcher(viteDevServer) {
   const path = '/';
   process.env.VITE_DEV_SERVER_URL = `${protocol}//${host}:${port}${path}`;
 
-  /** @type {import('child_process').ChildProcessWithoutNullStreams | null} */
+  /** @type {import('child_process').ChildProcessByStdio<null, null, import('stream').Readable> | null} */
   let spawnProcess = null;
 
   return setupEsbuildWatcher(
diff --git a/tsconfig.json b/tsconfig.json
index dfffc9d..255f334 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,7 +1,7 @@
 {
   "compilerOptions": {
-    "module": "es2022",
-    "target": "es2021",
+    "module": "esnext",
+    "target": "esnext",
     "moduleResolution": "node",
     "esModuleInterop": true,
     "allowSyntheticDefaultImports": true,
diff --git a/yarn.lock b/yarn.lock
index 15e8ac9..12a41fc 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1203,10 +1203,11 @@ __metadata:
     "@types/lodash-es": ^4.17.5
     "@types/ms": ^0.7.31
     "@types/node": ^17.0.5
-    chalk: ^5.0.0
+    chalk: ^4.1.2
     electron: 16.0.5
     electron-devtools-installer: ^3.2.0
     esbuild: ^0.14.9
+    jest: ^27.4.5
     json5: ^2.2.0
     lodash-es: ^4.17.21
     loglevel: ^1.8.0
@@ -1224,7 +1225,7 @@ __metadata:
   resolution: "@sophie/preload@workspace:packages/preload"
   dependencies:
     "@sophie/shared": "workspace:*"
-    "@types/jest": ^27.0.3
+    "@types/jest": ^27.4.0
     electron: 16.0.5
     jest: ^27.4.5
     jest-mock: ^27.4.2
@@ -1261,7 +1262,7 @@ __metadata:
     remotedev: ^0.2.9
     rimraf: ^3.0.2
     typescript: ^4.5.4
-    vite: ^2.7.9
+    vite: ^2.7.10
   languageName: unknown
   linkType: soft
 
@@ -1441,13 +1442,13 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@types/jest@npm:^27.0.3":
-  version: 27.0.3
-  resolution: "@types/jest@npm:27.0.3"
+"@types/jest@npm:^27.4.0":
+  version: 27.4.0
+  resolution: "@types/jest@npm:27.4.0"
   dependencies:
     jest-diff: ^27.0.0
     pretty-format: ^27.0.0
-  checksum: 3683a9945821966f6dccddf337219a5d682633687c9d30df859223db553589f63e9b2c34e69f0cc845c86ffcf115742f25c12ea03c8d33d2244890fdc0af61e2
+  checksum: d2350267f954f9a2e4a15e5f02fbf19a77abfb9fd9e57a954de1fb0e9a0d3d5f8d3646ac7d9c42aeb4b4d828d2e70624ec149c85bb50a48634a54eed8429e1f8
   languageName: node
   linkType: hard
 
@@ -2344,7 +2345,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"chalk@npm:^4.0.0, chalk@npm:^4.1.0, chalk@npm:^4.1.1":
+"chalk@npm:^4.0.0, chalk@npm:^4.1.0, chalk@npm:^4.1.1, chalk@npm:^4.1.2":
   version: 4.1.2
   resolution: "chalk@npm:4.1.2"
   dependencies:
@@ -2354,13 +2355,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"chalk@npm:^5.0.0":
-  version: 5.0.0
-  resolution: "chalk@npm:5.0.0"
-  checksum: 6eba7c518b9aa5fe882ae6d14a1ffa58c418d72a3faa7f72af56641f1bbef51b645fca1d6e05d42357b7d3c846cd504c0b7b64d12309cdd07867e3b4411e0d01
-  languageName: node
-  linkType: hard
-
 "char-regex@npm:^1.0.2":
   version: 1.0.2
   resolution: "char-regex@npm:1.0.2"
@@ -7001,7 +6995,7 @@ __metadata:
   resolution: "sophie@workspace:."
   dependencies:
     "@electron/fuses": ^1.5.0
-    "@types/jest": ^27.0.3
+    "@types/jest": ^27.4.0
     "@vitejs/plugin-react": ^1.1.3
     chokidar: ^3.5.2
     cross-env: ^7.0.3
@@ -7016,7 +7010,7 @@ __metadata:
     rollup: ^2.62.0
     ts-jest: ^27.1.2
     typescript: ^4.5.4
-    vite: ^2.7.9
+    vite: ^2.7.10
   languageName: unknown
   linkType: soft
 
@@ -7673,9 +7667,9 @@ __metadata:
   languageName: node
   linkType: hard
 
-"vite@npm:^2.7.9":
-  version: 2.7.9
-  resolution: "vite@npm:2.7.9"
+"vite@npm:^2.7.10":
+  version: 2.7.10
+  resolution: "vite@npm:2.7.10"
   dependencies:
     esbuild: ^0.13.12
     fsevents: ~2.3.2
@@ -7698,7 +7692,7 @@ __metadata:
       optional: true
   bin:
     vite: bin/vite.js
-  checksum: 6a13e0678fec4d5811d4e1bc796a98644856e4d7a56b5e56dbe513834c871d2313a065e4b82469de910568c0d6c762133517c6b7bccff4514f9acf5ed47f1f61
+  checksum: 1757108547ca34bd01a8ee3973cb04b484492c9e5690fc75f54bbcbde5965ab6e0a5b8355c336adf0a9117aa0fdae3053af3aafa9e5eb783282fffa948cfbe11
   languageName: node
   linkType: hard