better notice

lib/util/settings.js

@@ -8,6 +8,18 @@ try {
   resolveDefaultConfigPathAlias = null;
 }
 
+const CAN_NOT_RESOLVE_TAILWIND_CONFIG_PATH_ERROR =
+  'Cannot resolve default tailwindcss config path. Please manually set the config option.';
+
+function notice() {
+  if (process.env.NODE_ENV !== 'test') {
+    console.warn(CAN_NOT_RESOLVE_TAILWIND_CONFIG_PATH_ERROR);
+    return {};
+  } else {
+    throw new Error(CAN_NOT_RESOLVE_TAILWIND_CONFIG_PATH_ERROR);
+  }
+}
+
 function getOption(context, name) {
   // Options (defined at rule level)
   const options = context.options[0] || {};
@@ -28,13 +40,11 @@ function getOption(context, name) {
       return '^class(Name)?$';
     case 'config':
       if (resolveDefaultConfigPathAlias === null) {
-        console.warn('Cannot resolve default config path. Please manually set the config option.');
-        return {};
+        return notice();
       } else {
         const path = resolveDefaultConfigPathAlias();
         if (!path) {
-          console.warn('Cannot resolve default config path. Please manually set the config option.');
-          return {};
+          return notice();
         }
         return path;
       }