chore(fastboot test config): allow object export with a deprecation warning

Author: gilest

lib/helpers.js

@@ -7,6 +7,7 @@ const { URL } = require('url');
 const JSONfn = require('json-fn');
 const FastBoot = require('fastboot');
 const bodyParser = require('body-parser');
+const { deprecate } = require('util');
 
 function createMockRequest(app) {
   app.post(
@@ -104,13 +105,15 @@ function makeFastbootTestingConfig(config, pkg) {
 
   if (fs.existsSync(fastbootTestConfigPath)) {
     const fastbootTestConfig = require(fastbootTestConfigPath);
-    if (typeof fastbootTestConfig !== 'function') {
-      throw new Error(
-        `Expected export of ${fastbootTestConfigPath} to be a function. Instead found (${typeof fastbootTestConfig}).`
-      );
-    }
 
-    customized = fastbootTestConfig();
+    if (typeof fastbootTestConfig === 'function') {
+      customized = fastbootTestConfig();
+    } else {
+      deprecate(
+        () => Object.assign(customized, fastbootTestConfig),
+        `Exporting an object from ${fastbootTestConfigPath} has been deprecated. Please export a function which returns an object instead.`,
+      )();
+    }
   }
 
   return Object.assign({}, config, defaults, customized);