test: Add terminal title resolver tests

Tests cover placeholder resolution, segment dropping for empty
placeholders, task file reading, string/object model formats,
and null return when all segments are empty.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: m-mcgowan

src/utils/__tests__/terminal-title.test.ts

@@ -0,0 +1,109 @@
+import { mkdirSync, rmSync, writeFileSync } from 'fs';
+import { tmpdir } from 'os';
+import { join } from 'path';
+import {
+    afterEach,
+    beforeEach,
+    describe,
+    expect,
+    it,
+    vi
+} from 'vitest';
+
+import type { RenderContext } from '../../types/RenderContext';
+
+// Mock homedir for task file reads
+vi.mock('os', async () => {
+    const actual = await vi.importActual('os');
+    return {
+        ...actual,
+        homedir: () => join(tmpdir(), 'ccstatusline-test-home')
+    };
+});
+
+// Mock git commands
+vi.mock('../git', () => ({
+    runGit: (cmd: string) => {
+        if (cmd === 'branch --show-current') return 'main';
+        if (cmd === 'rev-parse --show-toplevel') return '/Users/test/my-repo';
+        return null;
+    }
+}));
+
+// Import after mocks
+const { resolveTerminalTitle } = await import('../terminal-title');
+
+function taskDir(): string {
+    return join(tmpdir(), 'ccstatusline-test-home', '.cache', 'ccstatusline', 'tasks');
+}
+
+function writeTask(sessionId: string, data: Record<string, string>): void {
+    const dir = taskDir();
+    mkdirSync(dir, { recursive: true });
+    writeFileSync(join(dir, `claude-task-${sessionId}`), JSON.stringify(data), 'utf8');
+}
+
+const baseContext: RenderContext = {
+    data: {
+        session_id: 'test-session',
+        model: { display_name: 'Opus 4.6' },
+        workspace: { current_dir: '/Users/test/my-repo' }
+    }
+};
+
+describe('resolveTerminalTitle', () => {
+    beforeEach(() => {
+        mkdirSync(taskDir(), { recursive: true });
+    });
+
+    afterEach(() => {
+        try { rmSync(taskDir(), { recursive: true, force: true }); } catch { /* ignore */ }
+    });
+
+    it('resolves repo and branch', () => {
+        const result = resolveTerminalTitle('{repo}/{branch}', baseContext);
+        expect(result).toBe('my-repo/main');
+    });
+
+    it('resolves model', () => {
+        const result = resolveTerminalTitle('{model}', baseContext);
+        expect(result).toBe('Opus 4.6');
+    });
+
+    it('resolves dir', () => {
+        const result = resolveTerminalTitle('{dir}', baseContext);
+        expect(result).toBe('my-repo');
+    });
+
+    it('resolves task from file', () => {
+        writeTask('test-session', { task: 'Fix auth bug' });
+        const result = resolveTerminalTitle('{task}', baseContext);
+        expect(result).toBe('Fix auth bug');
+    });
+
+    it('drops empty segments', () => {
+        // No task file exists, so {task} is empty
+        const result = resolveTerminalTitle('{task} | {repo}/{branch}', baseContext);
+        expect(result).toBe('my-repo/main');
+    });
+
+    it('keeps both segments when task exists', () => {
+        writeTask('test-session', { task: 'Build API' });
+        const result = resolveTerminalTitle('{task} | {repo}/{branch}', baseContext);
+        expect(result).toBe('Build API | my-repo/main');
+    });
+
+    it('returns null when all segments are empty', () => {
+        const emptyContext: RenderContext = { data: {} };
+        const result = resolveTerminalTitle('{task}', emptyContext);
+        expect(result).toBeNull();
+    });
+
+    it('handles string model format', () => {
+        const ctx: RenderContext = {
+            data: { model: 'Claude Haiku' }
+        };
+        const result = resolveTerminalTitle('{model}', ctx);
+        expect(result).toBe('Claude Haiku');
+    });
+});