在 Typescript 中定义动态数组？

Question

I have a requirement where i want to read a particular value x(that is auto-generated everytime) in a loop of say n times. Now, i want to store these autogenerated values of x, so, that i can later use them and iterate over it to perform my tests(protractor).

The way, i am trying to do is by creating an Array, using let list: string[] = []; . Now, i am pushing the values to my defined list using, list.push[x]; in each iteration. By the end of loop expecting to get the resulting Array having n values of x(string) in my list array. In order to validate, i did console.log(list); in each iteration and i can see that these values are being pushed in the defined list .

Later, in my code if i am trying to access these elements using let item = list[0];i am getting the undefined value.

I think i need to initialize the Array to some particular size having default values initially and then modify them later in the loop. But, being new to TypeScript i am not able to find a solution on how to do it. Please help, TIA!!

Here, is the snippet below:

    const tests = [
{type: 'admin', id='', uname='foo', pass='bar'},
{type: 'super', id='', uname='foo1', pass='bar'},
{type: 'normal', id='customId', uname='foo', pass='bar'}
];

let list: string[] = [];
// let list = [         //this is the final list that i got from the console.log(list);
// 'QR417msytVrq',
// 'V0fxayA3FOBD',
// 'QnaiegiVoYhs'];

describe(`Open Page `, () => {
  //Code to get to the page

  beforeAll(async () => {
    //initialize page objects

  });

  describe(`Login User `, async () => {
    tests.forEach(test => {
      it(` should login user with `+test.type, async () => {

        //....
        //....


        // On Success
        const myId = userPage.getUID().getText();

        list.push(myId);
        console.log(list);
        console.log(list.length);
      });
    });
  });


  describe(`Delete User`, async () => {

    // describe(`Confirmation `, async () => {
    console.log(list);
    // list.forEach(item => {       //this code doesn't gets executed and wasn't giving any error, so, commented out and tried to access the first element which is undefined.
      let item = list[0];
      console.log(item);            //getting undefined value here. 
      it(` should select and Delete the User having id as ` + item, async () => {
        //code to remove the user having id as item.
      });
    // });
  });
});

Answer 1

Options to test deleting a user:

Ultimately, it's bad practice to make tests dependent on other tests .

That said, two or possibly three options which should work:

A: Iterate through list of users within one test

describe(`Delete User`, async () => {
    describe(`Confirmation `, () => {
        it(`Log all users out who previously logged in`, async () => {
            list.forEach((item) => {
                console.log(item);
            });
        });
    });
});

Since the list array is populated by the previous test, inserting the code dependent on it inside of the next test would ensure that it has values to work with.

B: Login and delete user in one test

describe(`Login and delete user `, async () => {
    tests.forEach(test => {
        it(` should login and delete user with ` + test.type, async () => {
            const myId = userPage.getUID().getText();
            // Select and delete myId here
        });
    });
});

You may be able to remove the list array entirely by putting the entirety of the user flow into one large integration test.

C: Use mock data (may not be applicable if data is random)

describe(`Delete User`, async () => {
    const list = ["QR417msytVrq", "V0fxayA3FOBD", "QnaiegiVoYhs"];
    describe(`Confirmation `, () => {
        list.forEach((item) => {
            it(
                ` should select and Delete the User having id as ` + item,
                async () => {}
            );
        });
    });
});

If you know what the values to delete are going to be ahead of time, you can add them in manually. If the values are randomly generated, this won't work.

Other problems:

Testing order of execution

The dynamic array syntax you're using looks right however you appear to have an order of execution problem in your tests.

The code in the describe functions that is outside of the specs (the it blocks) is executed before any of the code inside of the specs is. The testing framework will traverse the tree of describe blocks, executing any code it finds but only taking note of the it specs. When it's finished this, it then executes the it specs it found in sequential order.

When you attempt to save the value of list[0] , the 'Login User' specs have yet to be executed. More specifically:

describe(`Login User `, async () => {
    tests.forEach(test => {
        it(` should login user with ` + test.type, async () => {
            // This code is executed AFTER the code in the 'Delete User' 
            // block but BEFORE the 'Delete User' spec
            const myId = userPage.getUID().getText();
            list.push(myId);
        });
    });
});


describe(`Delete User`, async () => {
    // This code is executed before any specs are run
    let item = list[0];
    // List is [] when item is initialized
    // The following spec will therefore not work as item is undefined
    it(` should select and Delete the User having id as ` + item, async () => {
    });
});

A possible solution to this would be to change the string of the 'Delete User' spec to something like ' should select and Delete first User' as well as move all the code outside of the spec to inside.

Describe blocks should not return promises

Your code sample has describe blocks (specifically 'Login User' , 'Delete User' , and 'Confirmation' ) which return Promises. You should remove the async in front of the function declarations. The specs can and should remain the same. For example:

describe(`Login User `, () => {

Object syntax

The tests object at the start of your sample isn't using JS/TS object syntax. Each key should be followed by a colon before the value instead of an equals sign. You likely meant to write:

const tests = [{
        type: 'admin',
        id: '',
        uname: 'foo',
        pass: 'bar'
    },
    {
        type: 'super',
        id: '',
        uname: 'foo1',
        pass: 'bar'
    },
    {
        type: 'normal',
        id: 'customId',
        uname: 'foo',
        pass: 'bar'
    }
];

Sources:

• Jest docs describing order of execution
• SO on Promise returning in describe blocks