add dependencies, .babelrc and config files to make tests work on web…

…storm

.babelrc

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+{
+  "presets": ["@babel/preset-react"],
+  "plugins": [
+    "@babel/plugin-proposal-class-properties",
+    "@babel/plugin-proposal-object-rest-spread",
+    "@babel/plugin-syntax-dynamic-import",
+    ["@babel/plugin-proposal-decorators", { "legacy": true }]
+  ],
+  "env": {
+    "test": {
+      "presets": ["@babel/preset-env", "@babel/preset-react"]
+    }
+  }
+}

config/jest/cssTransform.js

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+'use strict';
+
+// This is a custom Jest transformer turning style imports into empty objects.
+// http://facebook.github.io/jest/docs/en/webpack.html
+
+module.exports = {
+  process() {
+    return 'module.exports = {};';
+  },
+  getCacheKey() {
+    // The output is always the same.
+    return 'cssTransform';
+  },
+};

config/jest/fileTransform.js

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+'use strict';
+
+const path = require('path');
+
+// This is a custom Jest transformer turning file imports into filenames.
+// http://facebook.github.io/jest/docs/en/webpack.html
+
+module.exports = {
+  process(src, filename) {
+    return `module.exports = ${JSON.stringify(path.basename(filename))};`;
+  },
+};

jest.config.js

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+module.exports = {
+  testMatch: [
+    '<rootDir>/src/**/__tests__/**/*.js?(x)',
+    '<rootDir>/src/**/?(*.)(spec|test).js?(x)'
+  ],
+  transform: {
+    '^.+\\.(js|jsx|mjs)$': '<rootDir>/node_modules/babel-jest',
+    '^.+\\.css$': '<rootDir>/config/jest/cssTransform.js',
+    '^(?!.*\\.(js|jsx|css|json)$)': '<rootDir>/config/jest/fileTransform.js'
+  }
+}