单元测试以获取角度4中的随机数

Question

I have a method in my ts file to create random list as below.

list = [];

createItem(index, random_boolean) {
    return { id: index, name: `Item ${index}`, details: `Item ${index} occured`, selected : random_boolean };
}
createRandomItem() {
    const int = parseInt((Math.random() * 100) + '', 10);
    const random_boolean  = Math.random() >= 0.5;
    return this.createItem(int, random_boolean);
  } 

for (var i = 0; i < 10; i++) {
    list.push(this.createRandomItem(i));
}

How to write unit test case for createRandomItem() method.

Thanks for the help.

Answer 1

You need to decide what specifically you are trying to test. You can probably trust that Math.random() has been tested and works as advertised, so you don't need to test that. After that, what are you left with? You can test that given two random numbers, your method does the right thing with them. To do that, you can mock Math.random() so it delivers predictable results and then assert the the returned object has the expected properties. If you are using Jasmine, it might look something like:

it("should return an object based on the result of Math.random()", function() {
    spyOn(Math, 'random').and.returnValues(0.1, 0.75);
    let t = obj.createRandomItem()
    expect(t).toEqual({ 
        id: 10,
        name: 'Item 10',
        details: 'Item 10 occured',
        selected: true }); 
});