Fix an issue where the combination of deepmerge and webpack breaks tests

src/common/deepmerge.js

@@ -0,0 +1,10 @@
+const deepmerge = require('deepmerge');
+
+function deepMergeProxy(x, y, options) {
+  if (process.env.TEST) {
+    return deepmerge(x, y, options);
+  }
+  return deepmerge.default(x, y, options); // due to webpack conversion
+}
+
+module.exports = deepMergeProxy;

src/common/settings.js

@@ -3,10 +3,7 @@
 const fs = require('fs');
 
 const path = require('path');
-let deepmerge = require('deepmerge').default;
-if (process.env.TEST) {
-  deepmerge = require('deepmerge'); // eslint-disable-line
-}
+const deepmerge = require('./deepmerge');
 
 const settingsVersion = 1;
 const baseConfig = require('./config/base.json');