handler.test.ts

import 'mocha';
import { expect } from 'chai';
import * as sinon from 'sinon';

import { DynamoDB } from 'aws-sdk';

import { handler } from '../../src/handlers/post-item';
import { ApiGatewayResponse } from '../../src/models/apigateway/apigateway-response';
import { ApiGatewayEventMock } from '../models/apigateway-event-mock';

describe('Lambda handler', () => {
    
    describe('Lambda handler validation', () => {
        it('should return a 422 status code when body is missing "id" field', async () => {
            const event = new ApiGatewayEventMock();
            event.body = '{ "title": "test", "isCompleted": "false"}';
            
            const lambdaResponse: ApiGatewayResponse = await handler(event);
            
            expect(lambdaResponse).to.have.property('statusCode');
            expect(lambdaResponse.statusCode).to.equal(422);
        });
        
        it('should return a 422 status code when body is missing "title" field', async () => {
            const event = new ApiGatewayEventMock();
            event.body = '{ "id": "1", "isCompleted": "false"}';
            
            const lambdaResponse: ApiGatewayResponse = await handler(event);
            
            expect(lambdaResponse).to.have.property('statusCode');
            expect(lambdaResponse.statusCode).to.equal(422);
        });
        
        it('should return a 422 status code when body is missing "isComplete" field', async () => {
            const event = new ApiGatewayEventMock();
            event.body = '{ "id": "1", "isCompleted": "false"}';
            
            const lambdaResponse: ApiGatewayResponse = await handler(event);
            
            expect(lambdaResponse).to.have.property('statusCode');
            expect(lambdaResponse.statusCode).to.equal(422);
        });
    });
});

handler.ts

import { DynamoDB } from 'aws-sdk';

import { ApiGatewayEvent } from '../models/apigateway/apigateway-event';
import { ApiGatewayResponse } from '../models/apigateway/apigateway-response';
import { TodoItem } from '../models/todo-item';

export const handler = async (event: ApiGatewayEvent): Promise<ApiGatewayResponse> => {

    try {
        const todo: TodoItem = JSON.parse(event.body);
        
        if (!todo.title) {
            return { statusCode: 422 };
        } else if (!todo.isComplete) {
            todo.isComplete = false;
        } else if (!todo.id) {
            return { statusCode: 422 };
        }
        
        const docClient = new DynamoDB.DocumentClient();
        const tableName = process.env['SAMPLE_TABLE'];
        if (!tableName) {
            console.log('SAMPLE_TABLE environment variable is missing');
            return { statusCode: 500 };
        }
        
        const params: DynamoDB.DocumentClient.PutItemInput = {
            TableName: tableName,
            Item: todo
        };
        
        await docClient.put(params).promise();
        return { statusCode: 201, body: todo };
        
    } catch(err) {
        console.log(err);
        return { statusCode: 500 };
    }
};