Add syncify helper for testing async functions that throw exceptions

src/test/index.js

@@ -2,3 +2,4 @@ export { requiredProps } from './required_props';
 export { takeMountedSnapshot } from './take_mounted_snapshot';
 export { findTestSubject } from './find_test_subject';
 export { startThrowingReactWarnings, stopThrowingReactWarnings } from './react_warnings';
+export { syncify } from './syncify';

src/test/syncify.js

@@ -0,0 +1,10 @@
+// Helper designed to help test async/await functions that throw exceptions
+// https://github.com/facebook/jest/issues/1377
+export const syncify = async (fn) => {
+  try {
+    const result = await fn();
+    return () => { return result; };
+  } catch (e) {
+    return () => { throw e; };
+  }
+};