Add failing test case for no-unused-modules and export { default } from.

Author: richardxia

Diff for: tests/src/rules/no-unused-modules.js

@@ -165,7 +165,11 @@ ruleTester.run('no-unused-modules', rule, {
 
 // // test for export from
 ruleTester.run('no-unused-modules', rule, {
-  valid: [],
+  valid: [
+    test({ options: unusedExportsOptions,
+           code: `export { default } from './file-o'`,
+           filename: testFilePath('./no-unused-modules/file-a.js')}),
+  ],
   invalid: [
     test({ options: unusedExportsOptions,
            code: `export { k } from '${testFilePath('./no-unused-modules/file-k.js')}'`,