From 2c739d0a0cb1a4648942fb234f168e2b8a01afc9 Mon Sep 17 00:00:00 2001
From: mic <m@micz.it>
Date: Fri, 20 Mar 2026 21:23:46 +0100
Subject: [PATCH] unit tets first try

---
 js/mzta-utils.js                |  14 +-
 package.json                    |  13 +
 tests/mzta-logger.test.js       |  59 +++
 tests/mzta-placeholders.test.js | 206 ++++++++++
 tests/mzta-prompts.test.js      |  98 +++++
 tests/mzta-utils-prompt.test.js |  73 ++++
 tests/mzta-utils.test.js        | 697 ++++++++++++++++++++++++++++++++
 tests/setup.js                  |  82 ++++
 vitest.config.js                |  21 +
 9 files changed, 1256 insertions(+), 7 deletions(-)
 create mode 100644 package.json
 create mode 100644 tests/mzta-logger.test.js
 create mode 100644 tests/mzta-placeholders.test.js
 create mode 100644 tests/mzta-prompts.test.js
 create mode 100644 tests/mzta-utils-prompt.test.js
 create mode 100644 tests/mzta-utils.test.js
 create mode 100644 tests/setup.js
 create mode 100644 vitest.config.js

diff --git a/js/mzta-utils.js b/js/mzta-utils.js
index c5dbc59e..30f93f50 100644
--- a/js/mzta-utils.js
+++ b/js/mzta-utils.js
@@ -45,7 +45,7 @@ export function getMiczItUrl(path) {
   return `https://micz.it/${prefix}${path}`;
 }
 
-function fixMsgHeader(msgHeader) {
+export function fixMsgHeader(msgHeader) {
   if (!msgHeader.bccList) {
     msgHeader.bccList = [];
   }
@@ -117,7 +117,7 @@ export async function getCurrentIdentity(msgHeader, getFull = false) {
 }
 
 
-function extractEmail(text) {
+export function extractEmail(text) {
   if((text=='')||(text==undefined)) return '';
   const emailRegex = /[\w.-]+@[\w.-]+\.\w+/;
   const match = text.match(emailRegex);
@@ -278,7 +278,7 @@ export function convertNewlinesToBr(text) {
   return text.replace(/\r\n/g, '\n').replace(/\n/g, '<br>');
 }
 
-function convertBrToNewlines(html) {
+export function convertBrToNewlines(html) {
   return html.replace(/<br\s*\/?>/gi, '\n');
 }
 
@@ -374,7 +374,7 @@ export function i18nConditionalGet(str) {
   return str; // Return the original string if the conditions are not met
 }
 
-function compareThunderbirdVersions(v1, v2) {
+export function compareThunderbirdVersions(v1, v2) {
   const v1parts = v1.split('.').map(Number);
   const v2parts = v2.split('.').map(Number);
 
@@ -472,7 +472,7 @@ export async function assignTagsToMessage(messageId, tags) {
   }
 }
 
-function getTagsKeyFromLabel(tag_names, all_tags_list) {
+export function getTagsKeyFromLabel(tag_names, all_tags_list) {
   const result = [];
 
   tag_names.forEach(name => {
@@ -488,7 +488,7 @@ function getTagsKeyFromLabel(tag_names, all_tags_list) {
   return result;
 }
 
-function sanitizeString(input) {
+export function sanitizeString(input) {
   // Define the regex to match valid characters
   const validChar = /^[^ ()/{%*<>"]+$/;
   // Filter out invalid characters from the string
@@ -799,7 +799,7 @@ export async function getLocalStorageUsedSpace(){
   return formatBytes(customprompts_space);
 }
 
-function formatBytes(bytes, decimals = 2) {
+export function formatBytes(bytes, decimals = 2) {
   if (bytes === 0) return '0 Bytes';
   const step = 1024;
   const suffixes = ['Bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
diff --git a/package.json b/package.json
new file mode 100644
index 00000000..6febc6a7
--- /dev/null
+++ b/package.json
@@ -0,0 +1,13 @@
+{
+  "private": true,
+  "description": "Dev-only: unit tests for ThunderAI. Not used by the addon.",
+  "type": "module",
+  "scripts": {
+    "test": "vitest run",
+    "test:watch": "vitest"
+  },
+  "devDependencies": {
+    "vitest": "^3.1.1",
+    "jsdom": "^26.1.0"
+  }
+}
diff --git a/tests/mzta-logger.test.js b/tests/mzta-logger.test.js
new file mode 100644
index 00000000..bab18f22
--- /dev/null
+++ b/tests/mzta-logger.test.js
@@ -0,0 +1,59 @@
+import { taLogger } from '../js/mzta-logger.js';
+
+describe('taLogger', () => {
+  let logSpy, errorSpy, warnSpy;
+
+  beforeEach(() => {
+    logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    errorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+    warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('sets prefix and debug flag in constructor', () => {
+    const logger = new taLogger('Test', true);
+    expect(logger.prefix).toBe('[ThunderAI Logger | Test] ');
+    expect(logger.do_debug).toBe(true);
+  });
+
+  it('log() outputs when debug is true', () => {
+    const logger = new taLogger('Test', true);
+    logger.log('hello');
+    expect(logSpy).toHaveBeenCalledWith('[ThunderAI Logger | Test] hello');
+  });
+
+  it('log() is silent when debug is false', () => {
+    const logger = new taLogger('Test', false);
+    logger.log('hello');
+    expect(logSpy).not.toHaveBeenCalled();
+  });
+
+  it('log() with do_debug parameter changes debug state', () => {
+    const logger = new taLogger('Test', false);
+    logger.log('hello', true);
+    expect(logSpy).toHaveBeenCalledWith('[ThunderAI Logger | Test] hello');
+    expect(logger.do_debug).toBe(true);
+  });
+
+  it('error() always outputs regardless of debug flag', () => {
+    const logger = new taLogger('Test', false);
+    logger.error('something broke');
+    expect(errorSpy).toHaveBeenCalledWith('[ThunderAI Logger | Test] something broke');
+  });
+
+  it('warn() always outputs regardless of debug flag', () => {
+    const logger = new taLogger('Test', false);
+    logger.warn('watch out');
+    expect(warnSpy).toHaveBeenCalledWith('[ThunderAI Logger | Test] watch out');
+  });
+
+  it('changeDebug() updates the debug flag', () => {
+    const logger = new taLogger('Test', false);
+    expect(logger.do_debug).toBe(false);
+    logger.changeDebug(true);
+    expect(logger.do_debug).toBe(true);
+  });
+});
diff --git a/tests/mzta-placeholders.test.js b/tests/mzta-placeholders.test.js
new file mode 100644
index 00000000..bfda1f43
--- /dev/null
+++ b/tests/mzta-placeholders.test.js
@@ -0,0 +1,206 @@
+import {
+  mapPlaceholderToSuggestion,
+  prepareCustomDataPHsForExport,
+  placeholdersUtils,
+} from '../js/mzta-placeholders.js';
+
+// ─── mapPlaceholderToSuggestion ──────────────────────────────────
+
+describe('mapPlaceholderToSuggestion', () => {
+  it('transforms non-dynamic placeholder', () => {
+    const p = { id: 'mail_subject', type: 'default', is_dynamic: 0 };
+    expect(mapPlaceholderToSuggestion(p)).toEqual({
+      command: '{%mail_subject%}',
+      type: 'default',
+      is_dynamic: 0,
+    });
+  });
+
+  it('transforms dynamic placeholder (adds colon)', () => {
+    const p = { id: 'mail_headers', type: 'default', is_dynamic: 1 };
+    expect(mapPlaceholderToSuggestion(p)).toEqual({
+      command: '{%mail_headers:%}',
+      type: 'default',
+      is_dynamic: 1,
+    });
+  });
+});
+
+// ─── prepareCustomDataPHsForExport ───────────────────────────────
+
+describe('prepareCustomDataPHsForExport', () => {
+  it('removes idnum from non-default placeholders', () => {
+    const placeholders = [
+      { id: 'thunderai_custom_test', is_default: 0, idnum: 1, text: 'hello' },
+    ];
+    const result = prepareCustomDataPHsForExport(placeholders);
+    expect(result[0]).not.toHaveProperty('idnum');
+    expect(result[0].text).toBe('hello');
+  });
+
+  it('keeps idnum for default placeholders', () => {
+    const placeholders = [
+      { id: 'mail_subject', is_default: 1, idnum: 1 },
+    ];
+    const result = prepareCustomDataPHsForExport(placeholders);
+    expect(result[0].idnum).toBe(1);
+  });
+});
+
+// ─── placeholdersUtils ───────────────────────────────────────────
+
+describe('placeholdersUtils.validateCustomDataPH_ID', () => {
+  it('prepends prefix if missing', () => {
+    expect(placeholdersUtils.validateCustomDataPH_ID('my_ph')).toBe('thunderai_custom_my_ph');
+  });
+
+  it('returns unchanged if prefix already present', () => {
+    expect(placeholdersUtils.validateCustomDataPH_ID('thunderai_custom_my_ph')).toBe('thunderai_custom_my_ph');
+  });
+});
+
+describe('placeholdersUtils.stripCustomDataPH_ID_Prefix', () => {
+  it('removes prefix if present', () => {
+    expect(placeholdersUtils.stripCustomDataPH_ID_Prefix('thunderai_custom_my_ph')).toBe('my_ph');
+  });
+
+  it('returns unchanged if prefix not present', () => {
+    expect(placeholdersUtils.stripCustomDataPH_ID_Prefix('other_ph')).toBe('other_ph');
+  });
+});
+
+describe('placeholdersUtils.hasPlaceholder', () => {
+  it('detects any placeholder when no specific placeholder given', () => {
+    expect(placeholdersUtils.hasPlaceholder('Hello {%mail_subject%}')).toBe(true);
+  });
+
+  it('returns false when no placeholder present', () => {
+    expect(placeholdersUtils.hasPlaceholder('Hello world')).toBe(false);
+  });
+
+  it('detects specific placeholder', () => {
+    expect(placeholdersUtils.hasPlaceholder('Text {%mail_subject%}', 'mail_subject')).toBe(true);
+  });
+
+  it('returns false for non-matching specific placeholder', () => {
+    expect(placeholdersUtils.hasPlaceholder('Text {%mail_subject%}', 'author')).toBe(false);
+  });
+
+  it('detects dynamic placeholder with value', () => {
+    expect(placeholdersUtils.hasPlaceholder('Header: {%mail_headers:X-Custom%}', 'mail_headers')).toBe(true);
+  });
+});
+
+describe('placeholdersUtils.hasCustomPlaceholder', () => {
+  it('detects thunderai_custom_ placeholders', () => {
+    expect(placeholdersUtils.hasCustomPlaceholder('Text {%thunderai_custom_myph%}')).toBe(true);
+  });
+
+  it('returns false when none present', () => {
+    expect(placeholdersUtils.hasCustomPlaceholder('Text {%mail_subject%}')).toBe(false);
+  });
+
+  it('checks specific custom placeholder', () => {
+    expect(placeholdersUtils.hasCustomPlaceholder('{%thunderai_custom_test%}', 'thunderai_custom_test')).toBe(true);
+    expect(placeholdersUtils.hasCustomPlaceholder('{%thunderai_custom_other%}', 'thunderai_custom_test')).toBe(false);
+  });
+});
+
+describe('placeholdersUtils.getPlaceholdersAdditionalTextArray', () => {
+  it('extracts additional_text placeholders', () => {
+    const result = placeholdersUtils.getPlaceholdersAdditionalTextArray('Text {%additional_text%}');
+    expect(result).toEqual([{ placeholder: '{%additional_text%}', info: '' }]);
+  });
+
+  it('extracts additional_text with custom info', () => {
+    const result = placeholdersUtils.getPlaceholdersAdditionalTextArray('Text {%additional_text:Subject line%}');
+    expect(result).toEqual([{ placeholder: '{%additional_text:Subject line%}', info: 'Subject line' }]);
+  });
+
+  it('deduplicates entries with same info', () => {
+    const text = '{%additional_text:#1%} and {%additional_text:#1%}';
+    const result = placeholdersUtils.getPlaceholdersAdditionalTextArray(text);
+    expect(result).toHaveLength(1);
+  });
+
+  it('returns multiple entries with different info', () => {
+    const text = '{%additional_text:#1%} and {%additional_text:#2%}';
+    const result = placeholdersUtils.getPlaceholdersAdditionalTextArray(text);
+    expect(result).toHaveLength(2);
+  });
+
+  it('returns empty array when none found', () => {
+    expect(placeholdersUtils.getPlaceholdersAdditionalTextArray('no placeholders')).toEqual([]);
+  });
+});
+
+describe('placeholdersUtils.failSafePlaceholders', () => {
+  it('returns empty string for null', () => {
+    expect(placeholdersUtils.failSafePlaceholders(null)).toBe('');
+  });
+
+  it('returns empty string for undefined', () => {
+    expect(placeholdersUtils.failSafePlaceholders(undefined)).toBe('');
+  });
+
+  it('passes through strings unchanged', () => {
+    expect(placeholdersUtils.failSafePlaceholders('hello')).toBe('hello');
+  });
+
+  it('passes through numbers unchanged', () => {
+    expect(placeholdersUtils.failSafePlaceholders(42)).toBe(42);
+  });
+
+  it('passes through empty string', () => {
+    expect(placeholdersUtils.failSafePlaceholders('')).toBe('');
+  });
+});
+
+describe('placeholdersUtils.replacePlaceholders', () => {
+  it('replaces known placeholders with provided values', () => {
+    const result = placeholdersUtils.replacePlaceholders({
+      text: 'Subject: {%mail_subject%}',
+      replacements: { mail_subject: 'Test Email' },
+    });
+    expect(result).toBe('Subject: Test Email');
+  });
+
+  it('replaces multiple placeholders', () => {
+    const result = placeholdersUtils.replacePlaceholders({
+      text: 'From: {%author%}, Subject: {%mail_subject%}',
+      replacements: { author: 'John', mail_subject: 'Hello' },
+    });
+    expect(result).toBe('From: John, Subject: Hello');
+  });
+
+  it('leaves unknown placeholders unchanged', () => {
+    const result = placeholdersUtils.replacePlaceholders({
+      text: 'Value: {%nonexistent_thing%}',
+      replacements: {},
+    });
+    expect(result).toBe('Value: {%nonexistent_thing%}');
+  });
+
+  it('skips additional_text when skip_additional_text is true', () => {
+    const result = placeholdersUtils.replacePlaceholders({
+      text: 'Text: {%additional_text%}',
+      replacements: { additional_text: 'replaced' },
+      skip_additional_text: true,
+    });
+    expect(result).toBe('Text: {%additional_text%}');
+  });
+
+  it('skips additional_text with suffix when skip_additional_text is true', () => {
+    const result = placeholdersUtils.replacePlaceholders({
+      text: 'Text: {%additional_text:#1%}',
+      replacements: {},
+      skip_additional_text: true,
+    });
+    expect(result).toBe('Text: {%additional_text:#1%}');
+  });
+
+  it('handles empty args gracefully', () => {
+    const result = placeholdersUtils.replacePlaceholders();
+    expect(result).toBe('');
+  });
+});
diff --git a/tests/mzta-prompts.test.js b/tests/mzta-prompts.test.js
new file mode 100644
index 00000000..9824cb4b
--- /dev/null
+++ b/tests/mzta-prompts.test.js
@@ -0,0 +1,98 @@
+import { preparePromptsForExport } from '../js/mzta-prompts.js';
+
+describe('preparePromptsForExport', () => {
+  // Helper: create a custom prompt with integration keys
+  function makeCustomPrompt(overrides = {}) {
+    return {
+      id: 'custom_1',
+      is_default: 0,
+      idnum: 5,
+      text: 'Do something',
+      enabled: 1,
+      api_type: '',
+      chatgpt_api_key: 'key1',
+      chatgpt_model: 'gpt-5',
+      ollama_host: 'http://localhost',
+      ollama_model: 'llama3',
+      ...overrides,
+    };
+  }
+
+  // Helper: create a default prompt
+  function makeDefaultPrompt(overrides = {}) {
+    return {
+      id: 'prompt_reply',
+      is_default: 1,
+      idnum: 1,
+      text: 'Reply to this email',
+      enabled: 1,
+      position_compose: 1,
+      position_display: 2,
+      need_custom_text: 0,
+      api_type: '',
+      chatgpt_api_key: 'key1',
+      chatgpt_model: 'gpt-5',
+      ollama_host: 'http://localhost',
+      ...overrides,
+    };
+  }
+
+  it('removes api_type and integration keys when include_api_settings is false', () => {
+    const prompts = [makeCustomPrompt()];
+    const result = preparePromptsForExport(prompts, false);
+    expect(result[0]).not.toHaveProperty('api_type');
+    expect(result[0]).not.toHaveProperty('chatgpt_api_key');
+    expect(result[0]).not.toHaveProperty('chatgpt_model');
+    expect(result[0]).not.toHaveProperty('ollama_host');
+    expect(result[0]).not.toHaveProperty('ollama_model');
+    expect(result[0].text).toBe('Do something');
+  });
+
+  it('removes idnum from custom prompts', () => {
+    const prompts = [makeCustomPrompt()];
+    const result = preparePromptsForExport(prompts, false);
+    expect(result[0]).not.toHaveProperty('idnum');
+  });
+
+  it('for default prompts, keeps only allowed keys when include_api_settings is false', () => {
+    const prompts = [makeDefaultPrompt()];
+    const result = preparePromptsForExport(prompts, false);
+    const keys = Object.keys(result[0]);
+    expect(keys).toContain('id');
+    expect(keys).toContain('enabled');
+    expect(keys).toContain('position_compose');
+    expect(keys).toContain('position_display');
+    expect(keys).toContain('need_custom_text');
+    expect(keys).not.toContain('text');
+    expect(keys).not.toContain('api_type');
+    expect(keys).not.toContain('chatgpt_api_key');
+  });
+
+  it('keeps api_type when include_api_settings is true', () => {
+    const prompts = [makeCustomPrompt({ api_type: 'chatgpt_api' })];
+    const result = preparePromptsForExport(prompts, true);
+    expect(result[0].api_type).toBe('chatgpt_api');
+  });
+
+  it('keeps only active integration keys when api_type is set and include_api_settings is true', () => {
+    const prompts = [makeCustomPrompt({ api_type: 'chatgpt_api' })];
+    const result = preparePromptsForExport(prompts, true);
+    // chatgpt keys should remain (active integration = "chatgpt" from "chatgpt_api")
+    expect(result[0]).toHaveProperty('chatgpt_api_key');
+    expect(result[0]).toHaveProperty('chatgpt_model');
+    // ollama keys should be removed
+    expect(result[0]).not.toHaveProperty('ollama_host');
+    expect(result[0]).not.toHaveProperty('ollama_model');
+  });
+
+  it('does not mutate the original array', () => {
+    const original = [makeCustomPrompt()];
+    const originalCopy = JSON.parse(JSON.stringify(original));
+    preparePromptsForExport(original, false);
+    expect(original).toEqual(originalCopy);
+  });
+
+  it('handles empty prompts array', () => {
+    expect(preparePromptsForExport([], false)).toEqual([]);
+  });
+});
diff --git a/tests/mzta-utils-prompt.test.js b/tests/mzta-utils-prompt.test.js
new file mode 100644
index 00000000..105b07bb
--- /dev/null
+++ b/tests/mzta-utils-prompt.test.js
@@ -0,0 +1,73 @@
+import { taPromptUtils } from '../js/mzta-utils-prompt.js';
+
+// ─── finalizePrompt_get_calendar_event ───────────────────────────
+
+describe('taPromptUtils.finalizePrompt_get_calendar_event', () => {
+  it('removes {%cc_list%} placeholder', () => {
+    const result = taPromptUtils.finalizePrompt_get_calendar_event('Send to {%cc_list%} please');
+    expect(result).toBe('Send to  please');
+  });
+
+  it('removes {%recipients%} placeholder', () => {
+    const result = taPromptUtils.finalizePrompt_get_calendar_event('Invite {%recipients%} now');
+    expect(result).toBe('Invite  now');
+  });
+
+  it('removes both placeholders', () => {
+    const result = taPromptUtils.finalizePrompt_get_calendar_event('To: {%recipients%}, CC: {%cc_list%}');
+    expect(result).toBe('To: , CC: ');
+  });
+
+  it('returns prompt unchanged if no placeholders present', () => {
+    const prompt = 'Create a calendar event from this email';
+    expect(taPromptUtils.finalizePrompt_get_calendar_event(prompt)).toBe(prompt);
+  });
+});
+
+// ─── getTagsFromResponse ─────────────────────────────────────────
+
+describe('taPromptUtils.getTagsFromResponse', () => {
+  it('parses JSON response with tags array', () => {
+    const response = '{"tags": ["urgent", "work"]}';
+    expect(taPromptUtils.getTagsFromResponse(response)).toEqual(['urgent', 'work']);
+  });
+
+  it('parses JSON response with tags as string', () => {
+    const response = '{"tags": "urgent, work"}';
+    expect(taPromptUtils.getTagsFromResponse(response)).toEqual(['urgent', 'work']);
+  });
+
+  it('handles JSON embedded in text', () => {
+    const response = 'Here are the tags: {"tags": ["a", "b"]} done';
+    expect(taPromptUtils.getTagsFromResponse(response)).toEqual(['a', 'b']);
+  });
+
+  it('falls back to comma splitting on invalid JSON', () => {
+    const response = 'urgent, work, personal';
+    expect(taPromptUtils.getTagsFromResponse(response)).toEqual(['urgent', 'work', 'personal']);
+  });
+
+  it('returns empty array for empty input', () => {
+    expect(taPromptUtils.getTagsFromResponse('')).toEqual([]);
+    expect(taPromptUtils.getTagsFromResponse(null)).toEqual([]);
+    expect(taPromptUtils.getTagsFromResponse(undefined)).toEqual([]);
+  });
+
+  it('filters tags when filter_tags is true', () => {
+    const response = '{"tags": ["urgent", "work", "personal"]}';
+    const result = taPromptUtils.getTagsFromResponse(response, true, 'urgent, personal');
+    expect(result).toEqual(['urgent', 'personal']);
+  });
+
+  it('filter is case-insensitive', () => {
+    const response = '{"tags": ["Urgent", "WORK"]}';
+    const result = taPromptUtils.getTagsFromResponse(response, true, 'urgent, work');
+    expect(result).toEqual(['Urgent', 'WORK']);
+  });
+
+  it('does not filter when filter_tags is false', () => {
+    const response = '{"tags": ["urgent", "work"]}';
+    const result = taPromptUtils.getTagsFromResponse(response, false, 'urgent');
+    expect(result).toEqual(['urgent', 'work']);
+  });
+});
diff --git a/tests/mzta-utils.test.js b/tests/mzta-utils.test.js
new file mode 100644
index 00000000..1baf1d06
--- /dev/null
+++ b/tests/mzta-utils.test.js
@@ -0,0 +1,697 @@
+import {
+  getLanguageDisplayName,
+  sanitizeHtml,
+  sanitizeMailHeaders,
+  stripHtmlKeepLines,
+  htmlBodyToPlainText,
+  cleanupNewlines,
+  convertNewlinesToBr,
+  convertNewlinesToParagraphs,
+  getGPTWebModelString,
+  getMenuContextCompose,
+  getMenuContextDisplay,
+  checkIfTagLabelExists,
+  normalizeStringList,
+  prepareOriginURL,
+  checkAPIIntegration,
+  hasSpecificIntegration,
+  extractJsonObject,
+  isAPIKeyValue,
+  validateChatGPTWebCustomData,
+  sanitizeChatGPTModelData,
+  sanitizeChatGPTWebCustomData,
+  getActiveSpecialPromptsIDs,
+  getConnectionType,
+  getMailBody,
+  generateCallID,
+  ChatGPTWeb_models,
+  fixMsgHeader,
+  extractEmail,
+  convertBrToNewlines,
+  compareThunderbirdVersions,
+  getTagsKeyFromLabel,
+  sanitizeString,
+  formatBytes,
+} from '../js/mzta-utils.js';
+
+// ─── Constants ───────────────────────────────────────────────────
+
+describe('ChatGPTWeb_models', () => {
+  it('is an array of model strings', () => {
+    expect(Array.isArray(ChatGPTWeb_models)).toBe(true);
+    expect(ChatGPTWeb_models.length).toBeGreaterThan(0);
+    ChatGPTWeb_models.forEach(m => expect(typeof m).toBe('string'));
+  });
+});
+
+describe('getMenuContextCompose', () => {
+  it('returns compose_action_menu', () => {
+    expect(getMenuContextCompose()).toBe('compose_action_menu');
+  });
+});
+
+describe('getMenuContextDisplay', () => {
+  it('returns message_display_action_menu', () => {
+    expect(getMenuContextDisplay()).toBe('message_display_action_menu');
+  });
+});
+
+// ─── String / HTML manipulation ──────────────────────────────────
+
+describe('sanitizeHtml', () => {
+  it('strips HTML tags but keeps <br>', () => {
+    expect(sanitizeHtml('<p>Hello</p><br>World')).toBe('Hello<br>World');
+  });
+
+  it('keeps <br/> and <br /> variants', () => {
+    expect(sanitizeHtml('A<br/>B<br />C')).toBe('A<br/>B<br />C');
+  });
+
+  it('passes through plain text unchanged', () => {
+    expect(sanitizeHtml('just text')).toBe('just text');
+  });
+
+  it('handles empty string', () => {
+    expect(sanitizeHtml('')).toBe('');
+  });
+
+  it('strips nested tags', () => {
+    expect(sanitizeHtml('<div><span>Hi</span></div>')).toBe('Hi');
+  });
+});
+
+describe('sanitizeMailHeaders', () => {
+  it('escapes < and > to HTML entities', () => {
+    expect(sanitizeMailHeaders('user@example.com <User Name>')).toBe('user@example.com &lt;User Name&gt;');
+  });
+
+  it('returns empty string for null/undefined/empty', () => {
+    expect(sanitizeMailHeaders(null)).toBe('');
+    expect(sanitizeMailHeaders(undefined)).toBe('');
+    expect(sanitizeMailHeaders('')).toBe('');
+  });
+
+  it('handles strings without angle brackets', () => {
+    expect(sanitizeMailHeaders('plain text')).toBe('plain text');
+  });
+});
+
+describe('stripHtmlKeepLines', () => {
+  it('converts </p> to newlines and removes <p>', () => {
+    expect(stripHtmlKeepLines('<p>line1</p><p>line2</p>')).toBe('line1\nline2');
+  });
+
+  it('converts <br> to newlines', () => {
+    expect(stripHtmlKeepLines('line1<br>line2')).toBe('line1\nline2');
+  });
+
+  it('removes other HTML tags', () => {
+    expect(stripHtmlKeepLines('<b>bold</b> <i>italic</i>')).toBe('bold italic');
+  });
+
+  it('trims result', () => {
+    expect(stripHtmlKeepLines('  <p>text</p>  ')).toBe('text');
+  });
+});
+
+describe('htmlBodyToPlainText', () => {
+  it('extracts text from simple HTML', () => {
+    expect(htmlBodyToPlainText('<p>Hello World</p>')).toBe('Hello World');
+  });
+
+  it('removes style elements', () => {
+    expect(htmlBodyToPlainText('<style>body{color:red}</style><p>text</p>')).toBe('text');
+  });
+
+  it('removes display:none elements', () => {
+    expect(htmlBodyToPlainText('<div style="display:none">hidden</div><p>visible</p>')).toBe('visible');
+  });
+
+  it('handles empty string', () => {
+    expect(htmlBodyToPlainText('')).toBe('');
+  });
+});
+
+describe('cleanupNewlines', () => {
+  it('normalizes \\r\\n to \\n', () => {
+    expect(cleanupNewlines('a\r\nb')).toBe('a\nb');
+  });
+
+  it('collapses multiple newlines to one', () => {
+    expect(cleanupNewlines('a\n\n\nb')).toBe('a\nb');
+  });
+
+  it('collapses spaces/tabs before newlines', () => {
+    expect(cleanupNewlines('a   \nb')).toBe('a\nb');
+  });
+
+  it('replaces &nbsp; with space', () => {
+    expect(cleanupNewlines('hello&nbsp;world')).toBe('hello world');
+  });
+
+  it('trims result', () => {
+    expect(cleanupNewlines('  text  ')).toBe('text');
+  });
+});
+
+describe('convertNewlinesToBr', () => {
+  it('converts \\n to <br>', () => {
+    expect(convertNewlinesToBr('a\nb')).toBe('a<br>b');
+  });
+
+  it('handles \\r\\n', () => {
+    expect(convertNewlinesToBr('a\r\nb')).toBe('a<br>b');
+  });
+
+  it('handles multiple newlines', () => {
+    expect(convertNewlinesToBr('a\n\nb')).toBe('a<br><br>b');
+  });
+});
+
+describe('convertNewlinesToParagraphs', () => {
+  it('wraps each line in <p> tags', () => {
+    expect(convertNewlinesToParagraphs('line1\nline2')).toBe('<p>line1</p><p>line2</p>');
+  });
+
+  it('handles single line', () => {
+    expect(convertNewlinesToParagraphs('single')).toBe('<p>single</p>');
+  });
+});
+
+describe('convertBrToNewlines', () => {
+  it('converts <br> to newlines', () => {
+    expect(convertBrToNewlines('a<br>b')).toBe('a\nb');
+  });
+
+  it('handles <br/> and <br /> variants', () => {
+    expect(convertBrToNewlines('a<br/>b<br />c')).toBe('a\nb\nc');
+  });
+
+  it('is case-insensitive', () => {
+    expect(convertBrToNewlines('a<BR>b<Br>c')).toBe('a\nb\nc');
+  });
+});
+
+// ─── Model / URL helpers ─────────────────────────────────────────
+
+describe('getGPTWebModelString', () => {
+  it('maps gpt-5 to "5"', () => {
+    expect(getGPTWebModelString('gpt-5')).toBe('5');
+  });
+
+  it('maps gpt-5-instant to "5 Fast"', () => {
+    expect(getGPTWebModelString('gpt-5-instant')).toBe('5 Fast');
+  });
+
+  it('maps gpt-5-t-mini to "5 Thinking mini"', () => {
+    expect(getGPTWebModelString('gpt-5-t-mini')).toBe('5 Thinking mini');
+  });
+
+  it('maps gpt-5-thinking to "5 Thinking"', () => {
+    expect(getGPTWebModelString('gpt-5-thinking')).toBe('5 Thinking');
+  });
+
+  it('returns model string for unknown models', () => {
+    expect(getGPTWebModelString('custom-model')).toBe('custom-model');
+  });
+
+  it('returns empty string for falsy input', () => {
+    expect(getGPTWebModelString(null)).toBe('');
+    expect(getGPTWebModelString('')).toBe('');
+    expect(getGPTWebModelString(undefined)).toBe('');
+  });
+
+  it('is case-insensitive and trims whitespace', () => {
+    expect(getGPTWebModelString('  GPT-5  ')).toBe('5');
+  });
+});
+
+describe('prepareOriginURL', () => {
+  it('appends /* to URL without trailing slash', () => {
+    expect(prepareOriginURL('https://example.com')).toBe('https://example.com/*');
+  });
+
+  it('appends * to URL with trailing slash', () => {
+    expect(prepareOriginURL('https://example.com/')).toBe('https://example.com/*');
+  });
+});
+
+// ─── Tag helpers ─────────────────────────────────────────────────
+
+describe('checkIfTagLabelExists', () => {
+  const tags = {
+    tag1: { tag: 'Important' },
+    tag2: { tag: 'Work' },
+    tag3: { tag: 'Personal' },
+  };
+
+  it('finds tag case-insensitively', () => {
+    expect(checkIfTagLabelExists('important', tags)).toBe(true);
+    expect(checkIfTagLabelExists('IMPORTANT', tags)).toBe(true);
+    expect(checkIfTagLabelExists('Important', tags)).toBe(true);
+  });
+
+  it('returns false when tag not found', () => {
+    expect(checkIfTagLabelExists('missing', tags)).toBe(false);
+  });
+
+  it('handles empty tags list', () => {
+    expect(checkIfTagLabelExists('any', {})).toBe(false);
+  });
+});
+
+describe('getTagsKeyFromLabel', () => {
+  const allTags = {
+    key1: { tag: 'Important' },
+    key2: { tag: 'Work' },
+    key3: { tag: 'Personal' },
+  };
+
+  it('returns keys for matching labels', () => {
+    expect(getTagsKeyFromLabel(['important', 'work'], allTags)).toEqual(['key1', 'key2']);
+  });
+
+  it('returns empty array for no matches', () => {
+    expect(getTagsKeyFromLabel(['missing'], allTags)).toEqual([]);
+  });
+
+  it('handles empty input', () => {
+    expect(getTagsKeyFromLabel([], allTags)).toEqual([]);
+  });
+});
+
+// ─── List / string utilities ─────────────────────────────────────
+
+describe('normalizeStringList', () => {
+  it('deduplicates and sorts comma-separated input', () => {
+    expect(normalizeStringList('b, a, c, a')).toBe('a, b, c');
+  });
+
+  it('deduplicates and sorts newline-separated input', () => {
+    expect(normalizeStringList('b\na\nc\na')).toBe('a, b, c');
+  });
+
+  it('returns comma-separated string by default (returnType=0)', () => {
+    expect(normalizeStringList('b, a', 0)).toBe('a, b');
+  });
+
+  it('returns newline-separated string (returnType=1)', () => {
+    expect(normalizeStringList('b, a', 1)).toBe('a\nb');
+  });
+
+  it('returns array (returnType=2)', () => {
+    expect(normalizeStringList('b, a', 2)).toEqual(['a', 'b']);
+  });
+
+  it('lowercases all items', () => {
+    expect(normalizeStringList('Apple, BANANA', 2)).toEqual(['apple', 'banana']);
+  });
+});
+
+describe('generateCallID', () => {
+  it('returns a string of the specified length', () => {
+    expect(generateCallID(10)).toHaveLength(10);
+    expect(generateCallID(20)).toHaveLength(20);
+  });
+
+  it('defaults to length 10', () => {
+    expect(generateCallID()).toHaveLength(10);
+  });
+
+  it('contains only alphanumeric characters', () => {
+    const id = generateCallID(100);
+    expect(id).toMatch(/^[A-Za-z0-9]+$/);
+  });
+});
+
+// ─── Boolean / logic helpers ─────────────────────────────────────
+
+describe('checkAPIIntegration', () => {
+  it('returns true for non-chatgpt_web connection types', () => {
+    expect(checkAPIIntegration('openai_api', false, null)).toBe(true);
+    expect(checkAPIIntegration('ollama', false, '')).toBe(true);
+  });
+
+  it('returns true for chatgpt_web with specific integration', () => {
+    expect(checkAPIIntegration('chatgpt_web', true, 'openai_api')).toBe(true);
+  });
+
+  it('returns false for chatgpt_web without specific integration', () => {
+    expect(checkAPIIntegration('chatgpt_web', false, null)).toBe(false);
+    expect(checkAPIIntegration('chatgpt_web', true, null)).toBe(false);
+    expect(checkAPIIntegration('chatgpt_web', true, '')).toBe(false);
+  });
+});
+
+describe('hasSpecificIntegration', () => {
+  it('returns true when use is true and conntype is non-empty', () => {
+    expect(hasSpecificIntegration(true, 'openai_api')).toBe(true);
+  });
+
+  it('returns false when use is false', () => {
+    expect(hasSpecificIntegration(false, 'openai_api')).toBe(false);
+  });
+
+  it('returns false when conntype is null or empty', () => {
+    expect(hasSpecificIntegration(true, null)).toBe(false);
+    expect(hasSpecificIntegration(true, '')).toBe(false);
+  });
+});
+
+describe('isAPIKeyValue', () => {
+  it('returns true for strings ending with _api_key', () => {
+    expect(isAPIKeyValue('openai_api_key')).toBe(true);
+    expect(isAPIKeyValue('chatgpt_api_key')).toBe(true);
+  });
+
+  it('returns false for other strings', () => {
+    expect(isAPIKeyValue('openai_model')).toBe(false);
+    expect(isAPIKeyValue('api_key_value')).toBe(false);
+  });
+});
+
+// ─── JSON extraction ─────────────────────────────────────────────
+
+describe('extractJsonObject', () => {
+  it('extracts JSON from string with surrounding text', () => {
+    const result = extractJsonObject('Here is the result: {"tags": ["a", "b"]} done');
+    expect(result).toEqual({ tags: ['a', 'b'] });
+  });
+
+  it('returns parsed object for valid JSON string', () => {
+    expect(extractJsonObject('{"key": "value"}')).toEqual({ key: 'value' });
+  });
+
+  it('extracts nested JSON', () => {
+    const result = extractJsonObject('text {"a": {"b": 1}} more');
+    expect(result).toEqual({ a: { b: 1 } });
+  });
+
+  it('throws on no JSON found', () => {
+    expect(() => extractJsonObject('no json here')).toThrow('No JSON object found');
+  });
+
+  it('throws on invalid JSON', () => {
+    expect(() => extractJsonObject('{invalid json}')).toThrow();
+  });
+});
+
+// ─── ChatGPT validation / sanitization ───────────────────────────
+
+describe('validateChatGPTWebCustomData', () => {
+  it('validates /g/ paths with alphanumeric chars', () => {
+    expect(validateChatGPTWebCustomData('/g/abc-123')).toBe(true);
+    expect(validateChatGPTWebCustomData('/g/my-gpt/test')).toBe(true);
+  });
+
+  it('rejects invalid paths', () => {
+    expect(validateChatGPTWebCustomData('invalid')).toBe(false);
+    expect(validateChatGPTWebCustomData('/g/')).toBe(false);
+    expect(validateChatGPTWebCustomData('/g/test space')).toBe(false);
+  });
+
+  it('accepts empty string', () => {
+    expect(validateChatGPTWebCustomData('')).toBe(true);
+  });
+});
+
+describe('sanitizeChatGPTModelData', () => {
+  it('encodes and lowercases input', () => {
+    expect(sanitizeChatGPTModelData('GPT-5')).toBe('gpt-5');
+  });
+
+  it('encodes special characters', () => {
+    expect(sanitizeChatGPTModelData('model name')).toBe('model%20name');
+  });
+
+  it('returns empty string for falsy input', () => {
+    expect(sanitizeChatGPTModelData(null)).toBe('');
+    expect(sanitizeChatGPTModelData('')).toBe('');
+    expect(sanitizeChatGPTModelData(undefined)).toBe('');
+  });
+});
+
+describe('sanitizeChatGPTWebCustomData', () => {
+  it('removes non-alphanumeric/dash/slash characters', () => {
+    expect(sanitizeChatGPTWebCustomData('/g/test-path')).toBe('/g/test-path');
+    expect(sanitizeChatGPTWebCustomData('/g/test path!')).toBe('/g/testpath');
+  });
+
+  it('returns empty string for falsy input', () => {
+    expect(sanitizeChatGPTWebCustomData(null)).toBe('');
+    expect(sanitizeChatGPTWebCustomData('')).toBe('');
+  });
+});
+
+// ─── Special prompts ─────────────────────────────────────────────
+
+describe('getActiveSpecialPromptsIDs', () => {
+  it('returns empty array with all false', () => {
+    expect(getActiveSpecialPromptsIDs({})).toEqual([]);
+  });
+
+  it('includes prompt_add_tags when addtags is true', () => {
+    const result = getActiveSpecialPromptsIDs({ addtags: true });
+    expect(result).toContain('prompt_add_tags');
+  });
+
+  it('includes calendar and task prompts when enabled', () => {
+    const result = getActiveSpecialPromptsIDs({
+      get_calendar_event: true,
+      get_calendar_event_from_clipboard: true,
+      get_task: true,
+    });
+    expect(result).toContain('prompt_get_calendar_event');
+    expect(result).toContain('prompt_get_calendar_event_from_clipboard');
+    expect(result).toContain('prompt_get_task');
+  });
+
+  it('on chatgpt_web: only includes add_tags if both addtags and addtags_api', () => {
+    const result = getActiveSpecialPromptsIDs({
+      is_chatgpt_web: true,
+      addtags: true,
+      addtags_api: true,
+    });
+    expect(result).toEqual(['prompt_add_tags']);
+  });
+
+  it('on chatgpt_web: excludes add_tags if addtags_api is false', () => {
+    const result = getActiveSpecialPromptsIDs({
+      is_chatgpt_web: true,
+      addtags: true,
+      addtags_api: false,
+    });
+    expect(result).toEqual([]);
+  });
+
+  it('on chatgpt_web: excludes calendar/task prompts', () => {
+    const result = getActiveSpecialPromptsIDs({
+      is_chatgpt_web: true,
+      get_calendar_event: true,
+      get_task: true,
+    });
+    expect(result).toEqual([]);
+  });
+});
+
+// ─── getConnectionType ───────────────────────────────────────────
+
+describe('getConnectionType', () => {
+  it('returns default connection_type when no prefix', () => {
+    const prefs = { connection_type: 'openai_api' };
+    expect(getConnectionType(prefs, null)).toBe('openai_api');
+  });
+
+  it('returns prompt api_type when no specific type and prompt has api_type', () => {
+    const prefs = { connection_type: 'openai_api' };
+    const prompt = { api_type: 'ollama_api' };
+    expect(getConnectionType(prefs, prompt)).toBe('ollama_api');
+  });
+
+  it('returns default when prefs is null', () => {
+    expect(getConnectionType(null, null)).toBe('');
+  });
+
+  it('returns prompt api_type over default when prompt has api_type', () => {
+    const prefs = { connection_type: 'openai_api' };
+    const prompt = { api_type: 'claude_api' };
+    expect(getConnectionType(prefs, prompt)).toBe('claude_api');
+  });
+});
+
+// ─── getMailBody ─────────────────────────────────────────────────
+
+describe('getMailBody', () => {
+  it('extracts text and html from message parts', () => {
+    const msg = {
+      parts: [
+        { contentType: 'text/plain', body: 'Hello plain' },
+        { contentType: 'text/html', body: '<p>Hello html</p>' },
+      ],
+    };
+    expect(getMailBody(msg)).toEqual({ text: 'Hello plain', html: '<p>Hello html</p>' });
+  });
+
+  it('converts text to html with <br> if no html part', () => {
+    const msg = {
+      parts: [{ contentType: 'text/plain', body: 'line1\nline2' }],
+    };
+    expect(getMailBody(msg)).toEqual({ text: 'line1\nline2', html: 'line1<br>line2' });
+  });
+
+  it('handles nested parts', () => {
+    const msg = {
+      parts: [
+        {
+          contentType: 'multipart/alternative',
+          parts: [
+            { contentType: 'text/plain', body: 'nested text' },
+            { contentType: 'text/html', body: '<p>nested html</p>' },
+          ],
+        },
+      ],
+    };
+    expect(getMailBody(msg)).toEqual({ text: 'nested text', html: '<p>nested html</p>' });
+  });
+
+  it('returns empty strings when no parts', () => {
+    expect(getMailBody({ parts: [] })).toEqual({ text: '', html: '' });
+    expect(getMailBody({})).toEqual({ text: '', html: '' });
+  });
+});
+
+// ─── getLanguageDisplayName ──────────────────────────────────────
+
+describe('getLanguageDisplayName', () => {
+  it('returns capitalized language name', () => {
+    const name = getLanguageDisplayName('en');
+    expect(name).toBe('English');
+  });
+
+  it('returns localized name for other languages', () => {
+    const name = getLanguageDisplayName('fr');
+    expect(name.charAt(0)).toBe(name.charAt(0).toUpperCase());
+    expect(name.length).toBeGreaterThan(0);
+  });
+});
+
+// ─── fixMsgHeader ────────────────────────────────────────────────
+
+describe('fixMsgHeader', () => {
+  it('adds missing bccList, ccList, and recipients', () => {
+    const header = {};
+    const result = fixMsgHeader(header);
+    expect(result.bccList).toEqual([]);
+    expect(result.ccList).toEqual([]);
+    expect(result.recipients).toEqual([]);
+  });
+
+  it('preserves existing values', () => {
+    const header = {
+      bccList: ['a@b.com'],
+      ccList: ['c@d.com'],
+      recipients: ['e@f.com'],
+    };
+    const result = fixMsgHeader(header);
+    expect(result.bccList).toEqual(['a@b.com']);
+    expect(result.ccList).toEqual(['c@d.com']);
+    expect(result.recipients).toEqual(['e@f.com']);
+  });
+});
+
+// ─── extractEmail ────────────────────────────────────────────────
+
+describe('extractEmail', () => {
+  it('extracts email from text', () => {
+    expect(extractEmail('John Doe <john@example.com>')).toBe('john@example.com');
+  });
+
+  it('extracts first email when multiple present', () => {
+    expect(extractEmail('a@b.com and c@d.com')).toBe('a@b.com');
+  });
+
+  it('returns empty string for empty/undefined input', () => {
+    expect(extractEmail('')).toBe('');
+    expect(extractEmail(undefined)).toBe('');
+  });
+
+  it('returns empty string when no email found', () => {
+    expect(extractEmail('no email here')).toBe('');
+  });
+});
+
+// ─── compareThunderbirdVersions ──────────────────────────────────
+
+describe('compareThunderbirdVersions', () => {
+  it('returns 0 for equal versions', () => {
+    expect(compareThunderbirdVersions('128.0', '128.0')).toBe(0);
+  });
+
+  it('returns 1 when first version is greater', () => {
+    expect(compareThunderbirdVersions('129.0', '128.0')).toBe(1);
+  });
+
+  it('returns -1 when first version is lesser', () => {
+    expect(compareThunderbirdVersions('127.0', '128.0')).toBe(-1);
+  });
+
+  it('handles different length version strings', () => {
+    expect(compareThunderbirdVersions('128.0.1', '128.0')).toBe(1);
+    expect(compareThunderbirdVersions('128', '128.0.0')).toBe(0);
+  });
+
+  it('compares multi-segment versions correctly', () => {
+    expect(compareThunderbirdVersions('128.1.2', '128.1.3')).toBe(-1);
+  });
+});
+
+// ─── sanitizeString ──────────────────────────────────────────────
+
+describe('sanitizeString', () => {
+  it('lowercases and removes invalid characters', () => {
+    expect(sanitizeString('Hello World')).toBe('helloworld');
+  });
+
+  it('removes special characters like < > * "', () => {
+    expect(sanitizeString('test<>*"val')).toBe('testval');
+  });
+
+  it('encodes non-ASCII characters', () => {
+    const result = sanitizeString('café');
+    expect(result).toBe('cafu00e9');
+  });
+
+  it('truncates to 29 characters', () => {
+    const long = 'a'.repeat(50);
+    expect(sanitizeString(long)).toHaveLength(29);
+  });
+
+  it('handles empty string', () => {
+    expect(sanitizeString('')).toBe('');
+  });
+});
+
+// ─── formatBytes ─────────────────────────────────────────────────
+
+describe('formatBytes', () => {
+  it('returns "0 Bytes" for zero', () => {
+    expect(formatBytes(0)).toBe('0 Bytes');
+  });
+
+  it('formats bytes correctly', () => {
+    expect(formatBytes(500)).toBe('500.00 Bytes');
+  });
+
+  it('formats kilobytes correctly', () => {
+    expect(formatBytes(1024)).toBe('1.00 KB');
+  });
+
+  it('formats megabytes correctly', () => {
+    expect(formatBytes(1048576)).toBe('1.00 MB');
+  });
+
+  it('respects decimals parameter', () => {
+    expect(formatBytes(1500, 0)).toBe('1 KB');
+    expect(formatBytes(1500, 1)).toBe('1.5 KB');
+  });
+});
diff --git a/tests/setup.js b/tests/setup.js
new file mode 100644
index 00000000..7f4f313b
--- /dev/null
+++ b/tests/setup.js
@@ -0,0 +1,82 @@
+import { vi } from 'vitest';
+
+// Global mock for Thunderbird's browser.* WebExtension APIs
+const browser = {
+  i18n: {
+    getMessage: vi.fn((key) => `[${key}]`),
+    getUILanguage: vi.fn(() => 'en-US'),
+  },
+  accounts: {
+    list: vi.fn(async () => []),
+  },
+  storage: {
+    sync: {
+      get: vi.fn(async (defaults) => {
+        if (typeof defaults === 'object' && defaults !== null) {
+          return { ...defaults };
+        }
+        return {};
+      }),
+      set: vi.fn(async () => {}),
+      remove: vi.fn(async () => {}),
+    },
+    local: {
+      get: vi.fn(async (defaults) => {
+        if (typeof defaults === 'object' && defaults !== null) {
+          return { ...defaults };
+        }
+        return {};
+      }),
+      set: vi.fn(async () => {}),
+      remove: vi.fn(async () => {}),
+    },
+  },
+  messages: {
+    getFull: vi.fn(async () => ({ headers: {}, parts: [] })),
+    get: vi.fn(async () => ({ tags: [] })),
+    tags: {
+      list: vi.fn(async () => []),
+      create: vi.fn(async () => {}),
+    },
+    update: vi.fn(async () => {}),
+    listAttachments: vi.fn(async () => []),
+  },
+  tabs: {
+    query: vi.fn(async () => []),
+    create: vi.fn(async () => ({})),
+    update: vi.fn(async () => ({})),
+  },
+  compose: {
+    getComposeDetails: vi.fn(async () => ({ body: '', subject: '' })),
+    setComposeDetails: vi.fn(async () => {}),
+  },
+  permissions: {
+    contains: vi.fn(async () => false),
+    request: vi.fn(async () => true),
+  },
+  runtime: {
+    getURL: vi.fn((path) => `moz-extension://fake-id/${path}`),
+    sendMessage: vi.fn(async () => null),
+  },
+  mailTabs: {
+    getSelectedMessages: vi.fn(async () => ({ messages: [{ subject: '' }] })),
+  },
+};
+
+// Global mock for Thunderbird's messenger.* APIs
+const messenger = {
+  messageDisplay: {
+    getDisplayedMessage: vi.fn(async () => ({ subject: '' })),
+  },
+  compose: {
+    getComposeDetails: vi.fn(async () => ({ body: '' })),
+    setComposeDetails: vi.fn(async () => {}),
+  },
+  messages: {
+    continueList: vi.fn(async () => ({ messages: [] })),
+  },
+};
+
+// Attach to globalThis so module-level code can access them
+globalThis.browser = browser;
+globalThis.messenger = messenger;
diff --git a/vitest.config.js b/vitest.config.js
new file mode 100644
index 00000000..edfbbe39
--- /dev/null
+++ b/vitest.config.js
@@ -0,0 +1,21 @@
+import { defineConfig } from 'vitest/config';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+
+export default defineConfig({
+  test: {
+    environment: 'jsdom',
+    setupFiles: ['./tests/setup.js'],
+    include: ['tests/**/*.test.js'],
+    globals: true,
+  },
+  resolve: {
+    alias: {
+      // js/mzta-prompts.js imports from "../../options/mzta-options-default.js"
+      // which resolves outside the repo root in Node.js. This alias fixes it.
+      '../../options/mzta-options-default.js': path.resolve(__dirname, 'options/mzta-options-default.js'),
+    }
+  }
+});