src/stories/

index.stories.js

import React from "react";
import { addDecorator } from "@storybook/react";

import ProviderWrapper from "./Providers";
import MuiTheme from "../assets/MuiTheme";

const withProviders = story => <ProviderWrapper theme={MuiTheme}>{story()}</ProviderWrapper>;

addDecorator(withProviders);

Providers.js

import React from "react";
import { ThemeProvider as MuiThemeProvider } from "@material-ui/styles";

const ProviderWrapper = ({ children, theme }) => <MuiThemeProvider theme={theme}>{children}</MuiThemeProvider>;

export default ProviderWrapper;