feat(content): function signatures + test cases

backend/data/questions/additive-number.yaml

@@ -9,6 +9,30 @@ categories:
 patterns:
   - backtracking
 
+function_signature: "def is_additive_number(num: str) -> bool:"
+
+test_cases:
+  visible:
+    - input: { num: "112358" }
+      expected: true
+    - input: { num: "199100199" }
+      expected: true
+    - input: { num: "1023" }
+      expected: false
+  hidden:
+    - input: { num: "123" }
+      expected: true
+    - input: { num: "12" }
+      expected: false
+    - input: { num: "101" }
+      expected: true
+    - input: { num: "000" }
+      expected: true
+    - input: { num: "111" }
+      expected: false
+    - input: { num: "1212122436" }
+      expected: true
+
 description: |
   An **additive number** is a string whose digits can form an **additive sequence**.