test: add Heatmap component test

jest.config.ts

@@ -4,4 +4,5 @@ module.exports = {
 		'^.+\\.(ts|tsx)?$': 'ts-jest',
 		'^.+\\.(js|jsx)$': 'babel-jest',
 	},
+	testEnvironment: 'jsdom',
 }

src/heatmap/Heatmap.test.tsx

@@ -0,0 +1,12 @@
+import React from 'react'
+import { render } from '@testing-library/react'
+import { getRandomCount } from '../utils'
+import { DAYS_IN_YEAR } from '../constants'
+
+import Heatmap from './Heatmap'
+
+describe('Heatmap', () => {
+	test('renders the Heatmap component', () => {
+		render(<Heatmap count={getRandomCount(DAYS_IN_YEAR)} />)
+	})
+})

src/heatmap/Heatmap.tsx

@@ -12,7 +12,6 @@ import {
 	transformPixelsToNumber,
 } from '../utils'
 import styled from 'styled-components'
-import './Tooltip.css'
 
 export interface IProps {
 	/**