fix(curriculum): preventing hardcoding answers in lab-depth-first-search (#65507)

Co-authored-by: zaira <zairahira@gmail.com>
Co-authored-by: Zaira <33151350+zairahira@users.noreply.github.com>

curriculum/challenges/english/blocks/lab-depth-first-search/68d275dd800f404d22a07564.md

@@ -90,6 +90,36 @@ You should have a function named `dfs` that takes two arguments.
 `) })
 ```
 
+The `dfs` function should return the correct results.
+
+```js
+({ test: () => runPython(`
+  import random
+
+  def solve(g, s):
+      v, q = set(), [s]
+      while q:
+          u = q.pop()
+          if u not in v:
+              v.add(u)
+              q.extend([i for i, x in enumerate(g[u]) if x == 1 and i not in v])
+      return v
+
+  random.seed(0)
+
+  for _ in range(10):
+      n = 6
+      mat = [[0]*n for _ in range(n)]
+      for i in range(n):
+          for j in range(i+1, n):
+              if random.random() > 0.5:
+                  mat[i][j] = mat[j][i] = 1
+
+      start = random.randint(0, n-1)
+      assert set(dfs(mat, start)) == solve(mat, start), "Random graph check failed"
+`) })
+```
+
 # --seed--
 
 ## --seed-contents--