Fix setupTests extension

Author: jonmpqts

packages/react-scripts/config/paths.js

@@ -58,7 +58,7 @@ module.exports = {
   appPackageJson: resolveApp('package.json'),
   appSrc: resolveApp('src'),
   yarnLockFile: resolveApp('yarn.lock'),
-  testsSetup: resolveApp('src/setupTests.js'),
+  testsSetup: resolveApp('src/setupTests.ts'),
   appNodeModules: resolveApp('node_modules'),
   publicUrl: getPublicUrl(resolveApp('package.json')),
   servedPath: getServedPath(resolveApp('package.json')),
@@ -78,7 +78,7 @@ module.exports = {
   appPackageJson: resolveApp('package.json'),
   appSrc: resolveApp('src'),
   yarnLockFile: resolveApp('yarn.lock'),
-  testsSetup: resolveApp('src/setupTests.js'),
+  testsSetup: resolveApp('src/setupTests.ts'),
   appNodeModules: resolveApp('node_modules'),
   publicUrl: getPublicUrl(resolveApp('package.json')),
   servedPath: getServedPath(resolveApp('package.json')),
@@ -107,7 +107,7 @@ if (
     appPackageJson: resolveOwn('package.json'),
     appSrc: resolveOwn('template/src'),
     yarnLockFile: resolveOwn('template/yarn.lock'),
-    testsSetup: resolveOwn('template/src/setupTests.js'),
+    testsSetup: resolveOwn('template/src/setupTests.ts'),
     appNodeModules: resolveOwn('node_modules'),
     publicUrl: getPublicUrl(resolveOwn('package.json')),
     servedPath: getServedPath(resolveOwn('package.json')),

packages/react-scripts/scripts/utils/createJestConfig.js

@@ -17,7 +17,7 @@ module.exports = (resolve, rootDir) => {
   // Use this instead of `paths.testsSetup` to avoid putting
   // an absolute filename into configuration after ejecting.
   const setupTestsFile = fs.existsSync(paths.testsSetup)
-    ? '<rootDir>/src/setupTests.js'
+    ? '<rootDir>/src/setupTests.ts'
     : undefined;
 
   // TODO: I don't know if it's safe or not to just use / as path separator