When defining the .getData() method using property initializer syntax, it becomes bound to the class instance. However, since the handler function relies on the DynamoDBClient class through an import statement, creating an instance in the test case and passing it to the handler during its invocation is not feasible.
To address this, you can mock both the aws-sdk module and the DynamoDB.DocumentClient class along with its instance.
DynamoDBClient.ts:
import { DynamoDB } from 'aws-sdk';
function getConfig() {
return { mockDynamoDBEndpoint: '' };
}
interface Config {
mockDynamoDBEndpoint: string;
}
export default class DynamoDBClient {
private config: Config;
private client: DynamoDB.DocumentClient;
constructor() {
this.config = getConfig();
const dynamoDBClientConfig = this.config.mockDynamoDBEndpoint
? {
endpoint: this.config.mockDynamoDBEndpoint,
sslEnabled: false,
region: 'local',
}
: undefined;
this.client = new DynamoDB.DocumentClient(dynamoDBClientConfig);
}
getData = async (id: string): Promise<any> => {
const response = await this.client
.query({
TableName: 'tableName',
IndexName: 'tableIndex',
KeyConditionExpression: 'id= :id',
ExpressionAttributeValues: {
':id': id,
},
})
.promise();
return response;
};
}
handler.ts:
import DynamoDBClient from './DynamoDBClient';
interface APIGatewayProxyEvent {}
interface APIGatewayProxyResult {}
export const handler = async (event: APIGatewayProxyEvent): Promise<APIGatewayProxyResult> => {
let respData = await new DynamoDBClient().getData('123');
return { statusCode: 200, body: JSON.stringify(respData) };
};
handler.test.ts:
import { handler } from './handler';
import { DynamoDB } from 'aws-sdk';
const mDocumentClientInstance = {
query: jest.fn().mockReturnThis(),
promise: jest.fn(),
};
jest.mock('aws-sdk', () => {
return {
DynamoDB: {
DocumentClient: jest.fn(() => mDocumentClientInstance),
},
};
});
describe('69475890', () => {
afterEach(() => {
jest.clearAllMocks();
});
test('should pass', async () => {
mDocumentClientInstance.promise.mockResolvedValueOnce({});
const event = {};
const actual = await handler(event);
expect(actual).toEqual({ statusCode: 200, body: JSON.stringify({}) });
expect(DynamoDB.DocumentClient).toBeCalled();
expect(mDocumentClientInstance.query).toBeCalledWith({
TableName: 'tableName',
IndexName: 'tableIndex',
KeyConditionExpression: 'id= :id',
ExpressionAttributeValues: {
':id': '123',
},
});
expect(mDocumentClientInstance.promise).toBeCalled();
});
});
test result:
PASS examples/69475890/handler.test.ts (8.642 s)
69475890
✓ should pass (4 ms)
-------------------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
-------------------|---------|----------|---------|---------|-------------------
All files | 100 | 50 | 100 | 100 |
DynamoDBClient.ts | 100 | 50 | 100 | 100 | 18
handler.ts | 100 | 100 | 100 | 100 |
-------------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 9.231 s