https://github.com/mikaelvesavuori/tdd-demo

Test-driven development demo starter to build a DynamoDB item size calculator.
https://github.com/mikaelvesavuori/tdd-demo

demo dynamodb starter tdd test-driven-development

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Test-driven development demo starter to build a DynamoDB item size calculator.

• Host: GitHub
• URL: https://github.com/mikaelvesavuori/tdd-demo
• Owner: mikaelvesavuori
• Created: 2023-12-10T18:42:37.000Z (11 months ago)
• Default Branch: main
• Last Pushed: 2024-01-17T16:20:04.000Z (10 months ago)
• Last Synced: 2024-10-12T22:46:05.760Z (about 1 month ago)
• Topics: demo, dynamodb, starter, tdd, test-driven-development
• Language: TypeScript
• Homepage:
• Size: 42 KB
• Stars: 2
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Test-Driven Development demo: Build a DynamoDB item size calculator

This repo sets up a basic Node environment for doing test-driven development using TypeScript and Ava, together with ESLint and Prettier for extra flair.

Install with `npm install`, run all tests with `npm test`, and start the watch mode so you can run tests while developing by running `npm start`.

## Exercise

Of course you can do whatever you want, but if you want a real project, how about making a DynamoDB item size calculator?

I've already provided some starting code for the actual byte size stuff in the `start` folder if you want to do that particular demo.

Your exercise will be to replicate the basic parts of the behavior of this [online tool](https://zaccharles.github.io/dynamodb-calculator/), as far as it comes to calculating the actual item size in bytes.

Some resources for you:

- https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/CapacityUnitCalculations.html

- https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html

- https://zaccharles.github.io/dynamodb-calculator/

- https://zaccharles.medium.com/calculating-a-dynamodb-items-size-and-consumed-capacity-d1728942eb7c

Extra credit features:

- Warn about "longish" attribute names (over 10 characters)

- RCU consumption (eventual and strong consistencies + as part of transactional)

- WCU consumption (eventual and strong consistencies + as part of transactional)

## Some ideas to start you off

Here's a basic starting point if you're lost. Note that for the actual solution you'll want to use the `byte` function provided.

The source file, `src/DynamoDbItemSize.ts`:

```ts

export function DynamoDbItemSize(object: Record) {

  const result = JSON.stringify(object);

  console.log('Result:', result);

  return result.length;

}

```

The initial tests, `tests/DynamoDbItemSize.test.ts`:

```ts

import test from 'ava';

import { DynamoDbItemSize } from '../src/DynamoDbItemSize';

test('It should handle empty objects', (t) => {

  const expected = 2;

  const result = DynamoDbItemSize({});

  t.is(result, expected);

});

test('It should handle objects with a single key', (t) => {

  const expected = 16;

  const result = DynamoDbItemSize({ name: 'Harry' });

  t.is(result, expected);

});

test('It should handle objects with multiple keys', (t) => {

  const expected = 66;

  const result = DynamoDbItemSize({

    name: 'Harry',

    address: 'Cafe5to2, Bachman Street, Silent Hill'

  });

  t.is(result, expected);

});

```

## Test cases

- It should handle a basic item shape with a single key

- It should handle a basic item shape with multiple keys

- It should handle a DynamoDB item shape using a string

- It should handle a DynamoDB item shape using a positive number

- It should handle a DynamoDB item shape using a negative number

- It should handle a DynamoDB item shape using binary

- It should handle a DynamoDB item shape using a boolean

- It should handle a DynamoDB item shape using a null

- It should handle a DynamoDB item shape using a map

- It should handle a DynamoDB item shape using a list

- It should handle a DynamoDB item shape using a string set

- It should handle a DynamoDB item shape using a number set

- It should handle a DynamoDB item shape using a binary set