feat(content): hidden test cases

backend/data/questions/multiply-strings.yaml

@@ -9,6 +9,26 @@ categories:
 patterns:
   - two-pointers
 
+function_signature: "def multiply(num1: str, num2: str) -> str:"
+
+test_cases:
+  visible:
+    - input: { num1: "2", num2: "3" }
+      expected: "6"
+    - input: { num1: "123", num2: "456" }
+      expected: "56088"
+  hidden:
+    - input: { num1: "0", num2: "0" }
+      expected: "0"
+    - input: { num1: "999", num2: "0" }
+      expected: "0"
+    - input: { num1: "1", num2: "1" }
+      expected: "1"
+    - input: { num1: "99", num2: "99" }
+      expected: "9801"
+    - input: { num1: "12345", num2: "6789" }
+      expected: "83810205"
+
 description: |
   Given two non-negative integers `num1` and `num2` represented as strings, return the product of `num1` and `num2`, also represented as a string.