testcases:
  - name: "testcase 1"
    inputs:
    - 1 : ["MinStack", "push()", "push()", "pop()", "push()", "pop()", "push()", "min_number()"]
    - 2 : [null, 9, 3, null, 4, null, 5, null]
    output: 
    - 1 : [null, null, null, 3, null, 4, null, 5]
    
  - name: "testcase 2"
    inputs:
    - 1: ["MinStack", "push()", "push()", "pop()", "push()", "pop()", "min_number()"]
    - 2: [null, 5, 10, null, 23, null, null]
    output:
    - 1 : [null, null, null, 10, null, 23, 5]

  - name: "testcase 3"
    inputs:
    - 1 : ["MinStack", "push()", "pop()", "push()", "pop()", "push()", "push()", "pop()", "min_number()"]
    - 2 : [null, 2, null, 4, null, 6, -3, null, null]
    output: 
    - 1 : [null, null, 2, null, 4, null, null, -3, 6]
    
  - name: "testcase 4"
    inputs:
    - 1: ["MinStack", "push()", "pop()", "push()", "push()", "pop()", "push()", "pop()", "min_number()"]
    - 2: [null, 14, null, 66, 71, null, 50, null, null]
    output:
    - 1 : [null, null, 14, null, null, 71, null, 50, 66]

  - name: "testcase 5"
    inputs:
    - 1 : ["MinStack", "push()", "push()", "push()", "push()", "push()", "push()", "min_number()"]
    - 2 : [null, -2, 4, 5, 0, 1, -3, null]
    output:
    - 1 : [null, null, null, null, null, null, null, -3]