feat(content): hidden test cases

backend/data/questions/course-schedule.yaml

@@ -26,6 +26,12 @@ test_cases:
       expected: false
     - input: { num_courses: 5, prerequisites: [[1, 0], [2, 0], [3, 1], [4, 2]] }
       expected: true
+    - input: { num_courses: 3, prerequisites: [[0, 1], [0, 2], [1, 2]] }
+      expected: true
+    - input: { num_courses: 4, prerequisites: [] }
+      expected: true
+    - input: { num_courses: 3, prerequisites: [[0, 1], [1, 2], [2, 0]] }
+      expected: false
 
 description: |
   There are a total of `numCourses` courses you have to take, labeled from `0` to `numCourses - 1`. You are given an array `prerequisites` where `prerequisites[i] = [a`<sub>`i`</sub>`, b`<sub>`i`</sub>`]` indicates that you **must** take course `b`<sub>`i`</sub> first if you want to take course `a`<sub>`i`</sub>.