Don't create models in backups/import

ts/test-electron/backup/CircularMessageCache_test.ts

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+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import * as sinon from 'sinon';
+
+import { generateAci } from '../../types/ServiceId';
+import { type MessageAttributesType } from '../../model-types.d';
+import { CircularMessageCache } from '../../services/backups/util/CircularMessageCache';
+import { DataWriter } from '../../sql/Client';
+
+const OUR_ACI = generateAci();
+
+function createMessage(sentAt: number): MessageAttributesType {
+  return {
+    sent_at: sentAt,
+    received_at: sentAt,
+    timestamp: sentAt,
+
+    id: 'abc',
+    type: 'incoming' as const,
+    conversationId: 'cid',
+  };
+}
+
+describe('backup/attachments', () => {
+  let messageCache: CircularMessageCache;
+  let flush: sinon.SinonStub;
+
+  beforeEach(async () => {
+    await DataWriter.removeAll();
+    flush = sinon.stub();
+    messageCache = new CircularMessageCache({
+      size: 2,
+      flush,
+    });
+  });
+
+  afterEach(async () => {
+    await DataWriter.removeAll();
+  });
+
+  it('should return a cached message', async () => {
+    const message = createMessage(123);
+    messageCache.push(message);
+
+    const found = await messageCache.findBySentAt(123, () => true);
+    sinon.assert.notCalled(flush);
+    assert.strictEqual(found, message);
+  });
+
+  it('should purge message from cache on overflow', async () => {
+    messageCache.push(createMessage(123));
+    messageCache.push(createMessage(124));
+    messageCache.push(createMessage(125));
+
+    const found = await messageCache.findBySentAt(123, () => true);
+    sinon.assert.calledOnce(flush);
+    assert.isUndefined(found);
+  });
+
+  it('should find message in the database', async () => {
+    const message = createMessage(123);
+
+    await DataWriter.saveMessage(message, {
+      ourAci: OUR_ACI,
+      forceSave: true,
+    });
+
+    const found = await messageCache.findBySentAt(123, () => true);
+    sinon.assert.calledOnce(flush);
+    assert.deepStrictEqual(found, message);
+  });
+});