feat(content): function signatures + test cases

backend/data/questions/all-elements-in-two-binary-search-trees.yaml

@@ -10,6 +10,24 @@ patterns:
   - tree-traversal
   - two-pointers
 
+function_signature: "def get_all_elements(root1: TreeNode, root2: TreeNode) -> list[int]:"
+
+test_cases:
+  visible:
+    - input: { root1: [2, 1, 4], root2: [1, 0, 3] }
+      expected: [0, 1, 1, 2, 3, 4]
+    - input: { root1: [1, null, 8], root2: [8, 1] }
+      expected: [1, 1, 8, 8]
+  hidden:
+    - input: { root1: [], root2: [5, 1, 7] }
+      expected: [1, 5, 7]
+    - input: { root1: [1], root2: [] }
+      expected: [1]
+    - input: { root1: [], root2: [] }
+      expected: []
+    - input: { root1: [0, -10, 10], root2: [5, 1, 7, 0, 2] }
+      expected: [-10, 0, 0, 1, 2, 5, 7, 10]
+
 description: |
   Given two binary search trees `root1` and `root2`, return *a list containing all the integers from both trees sorted in **ascending** order*.