feat(content): hidden test cases

backend/data/questions/group-anagrams.yaml

@@ -27,6 +27,12 @@ test_cases:
       expected: [["", ""]]
     - input: { strs: ["listen", "silent", "enlist"] }
       expected: [["listen", "silent", "enlist"]]
+    - input: { strs: ["a", "b", "c"] }
+      expected: [["a"], ["b"], ["c"]]
+    - input: { strs: ["abc", "def", "ghi"] }
+      expected: [["abc"], ["def"], ["ghi"]]
+    - input: { strs: ["aab", "aba", "baa", "ab", "ba"] }
+      expected: [["aab", "aba", "baa"], ["ab", "ba"]]
 
 description: |
   Given an array of strings `strs`, group the **anagrams** together. You can return the answer in **any order**.