Add a negative test case for interface classes in require-returns-check

Author: l1bbcsg

test/rules/assertions/requireReturnsCheck.js

@@ -89,6 +89,23 @@ export default {
           message: 'JSDoc @returns declaration present but return expression not available in function.'
         }
       ]
+    },
+    {
+      code: `
+          class Foo {
+            /**
+             * @returns {string}
+             */
+            bar () {
+            }
+          }
+      `,
+      errors: [
+        {
+          line: 3,
+          message: 'JSDoc @returns declaration present but return expression not available in function.'
+        }
+      ]
     }
   ],
   valid: [