feat(scripts/test): add TypeScript support to Jest via ts-jest

Author: jrolfs

src/config/jest.config.js

@@ -1,5 +1,5 @@
 const path = require('path')
-const {ifAnyDep, hasFile, hasPkgProp, fromRoot} = require('../utils')
+const {ifAnyDep, hasAnyDep, hasFile, hasPkgProp, fromRoot} = require('../utils')
 
 const here = p => path.join(__dirname, p)
 
@@ -34,14 +34,19 @@ const jestConfig = {
     require.resolve('jest-watch-typeahead/filename'),
     require.resolve('jest-watch-typeahead/testname'),
   ],
+  transform: {},
+}
+
+if (hasAnyDep('ts-jest')) {
+  jestConfig.preset = 'ts-jest'
 }
 
 if (hasFile('tests/setup-env.js')) {
   jestConfig.setupFilesAfterEnv = [fromRoot('tests/setup-env.js')]
 }
 
 if (useBuiltInBabelConfig) {
-  jestConfig.transform = {'^.+\\.js$': here('./babel-transform')}
+  Object.assign(jestConfig.transform, {'^.+\\.js$': here('./babel-transform')})
 }
 
 module.exports = jestConfig

src/utils.js

@@ -176,6 +176,7 @@ module.exports = {
   hasFile,
   hasPkgProp,
   hasScript,
+  hasAnyDep,
   ifAnyDep,
   ifDep,
   ifDevDep,