feat(content): function signatures + test cases

backend/data/questions/add-two-integers.yaml

@@ -7,6 +7,26 @@ categories:
   - math
 patterns: []
 
+function_signature: "def sum(num1: int, num2: int) -> int:"
+
+test_cases:
+  visible:
+    - input: { num1: 12, num2: 5 }
+      expected: 17
+    - input: { num1: -10, num2: 4 }
+      expected: -6
+  hidden:
+    - input: { num1: 0, num2: 0 }
+      expected: 0
+    - input: { num1: -100, num2: 100 }
+      expected: 0
+    - input: { num1: 50, num2: 50 }
+      expected: 100
+    - input: { num1: -50, num2: -50 }
+      expected: -100
+    - input: { num1: 1, num2: -1 }
+      expected: 0
+
 description: |
   Given two integers `num1` and `num2`, return *the **sum** of the two integers*.