How to use ARC's / AWS' `client._doc.transactWrite()` method?

example.test.mjs

// Trying to implement field uniqueness as described in:
// https://aws.amazon.com/blogs/database/simulating-amazon-dynamodb-unique-constraints-using-transactions/

// Using:
// mocha: v10.2.0
// node: v18.18.2
// macOS: Sonoma v14.1 (23B74)


import sinon from 'sinon'; // sinon@17.0.1
import { expect } from 'chai'; // chai@4.3.10
import sandbox from '@architect/sandbox'; // @architect/sandbox@5.9.2
import arc from '@architect/functions'; // @architect/functions@7.0.0


describe('DynamoDB: UnknownOperationException: UnknownError', () => {
	let tables; // b/c describe() doesn't support `async` callbacks :(

	before(async () => {
		await sandbox.start({ quiet: true });
		tables = await arc.tables();
	});

	afterEach(() => {
		sinon.restore();
	});

	after(async () => {
		await sandbox.end();
	});

	describe('Using `.transactWrite()`', () => {
		it('Starts with empty db', async () => {
			const records = await tables.chocotaco.scan({});
			expect(records.Count).to.equal(0);
			expect(records.Items).to.eql([]);
			expect(records['$metadata'].httpStatusCode).to.equal(200);
		});

		it('Creates new record', async () => {
			const client = await arc.tables();
			const TableName = 'chocotaco';
			await client._doc.transactWrite({
				TransactItems: [
					{
						Put: {
							TableName,
							ConditionExpression: 'attribute_not_exists(pk)',
							Item: {
								pk: 'my-fake-pk',
								sk: 'my-fake-sk',
								username: 'fake-username',
								email: 'fake@example.com'
							}
						}
					},
					{
						Put: {
							TableName,
							ConditionExpression: 'attribute_not_exists(pk)',
							Item: {
								pk: 'unique-username:fake-username',
								sk: 'unique-username'
							}
						}
					},
					{
						Put: {
							TableName,
							ConditionExpression: 'attribute_not_exists(pk)',
							Item: {
								pk: 'unique-email:fake@example.com',
								sk: 'unique-email'
							}
						}
					}
				]
			});
		});
	});

	it('Delete record', async () => {
		const client = await arc.tables();
		const TableName = 'chocotaco';
		await client._doc.transactWrite({
			TransactItems: [
				{ Delete: { TableName, Key: { email: 'fake@example.com' } } },
				{ Delete: { TableName, Key: { email: 'alsofake@example.com' } } },
			]
		});
	});
});

output.txt

>>eval $(cat .env) npm run test:unit

> knuckles@0.0.0 test:unit
> mocha './src/**/*.test.?(m)js'



  DynamoDB: UnknownOperationException: UnknownError
    Using `.transactWrite()`
      ✔ Starts with empty db (509ms)
      1) Creates new record
      2) Delete record


  1 passing (1s)
  2 failing

  1) DynamoDB: UnknownOperationException: UnknownError
       Using `.transactWrite()`
         Creates new record:
     UnknownOperationException: UnknownError
      at throwDefaultError (node_modules/@smithy/smithy-client/dist-cjs/default-error-handler.js:8:22)
      at /Users/me/code/bust/knuckles/node_modules/@smithy/smithy-client/dist-cjs/default-error-handler.js:18:39
      at de_TransactWriteItemsCommandError (node_modules/@aws-sdk/client-dynamodb/dist-cjs/protocols/Aws_json1_0.js:2239:20)
      at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
      at async /Users/me/code/bust/knuckles/node_modules/@smithy/middleware-serde/dist-cjs/deserializerMiddleware.js:7:24
      at async /Users/me/code/bust/knuckles/node_modules/@aws-sdk/lib-dynamodb/dist-cjs/baseCommand/DynamoDBDocumentClientCommand.js:29:34
      at async /Users/me/code/bust/knuckles/node_modules/@aws-sdk/middleware-signing/dist-cjs/awsAuthMiddleware.js:14:20
      at async /Users/me/code/bust/knuckles/node_modules/@smithy/middleware-retry/dist-cjs/retryMiddleware.js:27:46
      at async /Users/me/code/bust/knuckles/node_modules/@aws-sdk/middleware-logger/dist-cjs/loggerMiddleware.js:7:26
      at async Context.<anonymous> (file:///Users/me/code/bust/knuckles/src/shared/db/client/example.test.mjs:39:4)

  2) DynamoDB: UnknownOperationException: UnknownError
       Using `.transactWrite()`
         Delete record:
     UnknownOperationException: UnknownError
      at throwDefaultError (node_modules/@smithy/smithy-client/dist-cjs/default-error-handler.js:8:22)
      at /Users/me/code/bust/knuckles/node_modules/@smithy/smithy-client/dist-cjs/default-error-handler.js:18:39
      at de_TransactWriteItemsCommandError (node_modules/@aws-sdk/client-dynamodb/dist-cjs/protocols/Aws_json1_0.js:2239:20)
      at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
      at async /Users/me/code/bust/knuckles/node_modules/@smithy/middleware-serde/dist-cjs/deserializerMiddleware.js:7:24
      at async /Users/me/code/bust/knuckles/node_modules/@aws-sdk/lib-dynamodb/dist-cjs/baseCommand/DynamoDBDocumentClientCommand.js:29:34
      at async /Users/me/code/bust/knuckles/node_modules/@aws-sdk/middleware-signing/dist-cjs/awsAuthMiddleware.js:14:20
      at async /Users/me/code/bust/knuckles/node_modules/@smithy/middleware-retry/dist-cjs/retryMiddleware.js:27:46
      at async /Users/me/code/bust/knuckles/node_modules/@aws-sdk/middleware-logger/dist-cjs/loggerMiddleware.js:7:26
      at async Context.<anonymous> (file:///Users/me/code/bust/knuckles/src/shared/db/client/example.test.mjs:80:4)