When running yarn jest transform-runtime
The packages/babel-plugin-transform-runtime/test/index.js tests fails with (not the backslashes \ -> //):

- var _classCallCheck = require("<CWD>/packages/babel-plugin-transform-runtime/node_modules/@babel/runtime/helpers/classCallCheck");
+ var _classCallCheck = require("<CWD>\\packages\\babel-plugin-transform-runtime\\node_modules\\@babel\\runtime/helpers/classCallCheck");

When running make test, all of these fail

• packages/babel-core/test/config-chain.js
• packages/babel-preset-env-standalone/test/babel-preset-env.js
• packages/babel-generator/test/index.js
• packages/babel-plugin-transform-react-jsx-source/test/index.js
• packages/babel-preset-react/test/preset-options.js
• packages/babel-plugin-transform-runtime/test/index.js
• packages/babel-preset-env/test/debug-fixtures.js
• packages/babel-generator/test/index.js

Windows 7 (x64)