export function visitorSpyPlugin() { let Once = jest.fn() let OnceExit = jest.fn() let Root = jest.fn() let AtRule = jest.fn() let Rule = jest.fn() let Comment = jest.fn() let Declaration = jest.fn() let plugin = Object.assign( function () { return { postcssPlugin: 'visitor-test', // These work fine Once, OnceExit, // These break Root, Rule, AtRule, Declaration, Comment, } }, { postcss: true } ) return { plugin, spies: { Once, OnceExit, Root, AtRule, Rule, Comment, Declaration, }, } }