Add Jest config files

config/jest/setupTests.ts

@@ -0,0 +1,5 @@
+// jest-dom adds custom jest matchers for asserting on DOM nodes.
+// allows you to do things like:
+// expect(element).toHaveTextContent(/react/i)
+// learn more: https://github.com/testing-library/jest-dom
+import '@testing-library/jest-dom';

config/jest/transforms/babelTransform.ts

@@ -0,0 +1,29 @@
+'use strict';
+
+const babelJest = require('babel-jest');
+
+const hasJsxRuntime = (() => {
+  if (process.env.DISABLE_NEW_JSX_TRANSFORM === 'true') {
+    return false;
+  }
+
+  try {
+    require.resolve('react/jsx-runtime');
+    return true;
+  } catch (e) {
+    return false;
+  }
+})();
+
+module.exports = babelJest.createTransformer({
+  presets: [
+    [
+      require.resolve('babel-preset-react-app'),
+      {
+        runtime: hasJsxRuntime ? 'automatic' : 'classic',
+      },
+    ],
+  ],
+  babelrc: false,
+  configFile: false,
+});

config/jest/transforms/fileTransform.ts

@@ -0,0 +1,40 @@
+'use strict';
+
+const path = require('path');
+const camelcase = require('camelcase');
+
+// 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) {
+    const assetFilename = JSON.stringify(path.basename(filename));
+
+    if (filename.match(/\.svg$/)) {
+      // Based on how SVGR generates a component name:
+      // https://github.com/smooth-code/svgr/blob/01b194cf967347d43d4cbe6b434404731b87cf27/packages/core/src/state.js#L6
+      const pascalCaseFilename = camelcase(path.parse(filename).name, {
+        pascalCase: true,
+      });
+      const componentName = `Svg${pascalCaseFilename}`;
+      return `const React = require('react');
+      module.exports = {
+        __esModule: true,
+        default: ${assetFilename},
+        ReactComponent: React.forwardRef(function ${componentName}(props, ref) {
+          return {
+            $$typeof: Symbol.for('react.element'),
+            type: 'svg',
+            ref: ref,
+            key: null,
+            props: Object.assign({}, props, {
+              children: ${assetFilename}
+            })
+          };
+        }),
+      };`;
+    }
+
+    return `module.exports = ${assetFilename};`;
+  },
+};