Exam (elaborations)
Advanced JS Questions And Answers Latest Update
- Course
- Angular
- Institution
- Stanford University
Advanced JS Questions And Answers Latest Update
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Solution 2024/2025Pepper
Advanced JS Questions And Answers Latest
Update
Why write test? ANS✔✔ As you begin writing more complicated functions
and larger applications, you're bound to make mistakes. Everyone does it,
even professional programmers. When your programs grow they can
become more difficult to reason about, and as hard as you may try it's
impossible to predict every bug in your program. Fixing bugs also has a
cost, as it can be quite easy for one fix to introduce bugs in other parts of
your application.
Is there any way to avoid our programs becoming more brittle and difficult
to maintain as they grow in complexity? Yes! The solution to this problem
lies in testing our code as thoroughly as possible.
, Solution 2024/2025
Pepper
This makes it easier to protect against bugs, and to ensure that you don't
introduce new bugs in your code as you add new features or rewrite old
ones.
What is Jasmine? ANS✔✔ a test runner and expectation/assertion library. We
will be using it to run all of our tests. A test runner is a tool that is
responsible for running tests that you write and logging the results of the
tests for you to see.
Main functions we'll see the most with tests are: ANS✔✔ describe, it, and
expect
describe ANS✔✔ this function is given to us by jasmine and it is what we use
to organize our tests. You can think of a describe function like talking to
someone and telling them "let me describe ____ to you." Very often when
you're writing unit tests, you'll have one describe block per function you're
testing
it ANS✔✔ this function lives inside of describe functions. Inside of these it
functions we make our expectations. Each it function corresponds to a test;
if one of our expectations inside of the it function isn't met, the test fails.
let's just look at an example written in plain old English. Here's how you
might scaffold some tests to check whether a planet in our solar system is
Earth:
describe "Earth"
it "is round"
it "is the third planet from the sun"
, Solution 2024/2025
Pepper
it "is the densest of all the planets"
expect ANS✔✔ this is a function given to us by jasmine. When combined
with describe and it, we can write tests that looks something like this:
describe "Earth"
it "is round"
expect (earth.isRound).toEqual(true)
it "is the third planet from the sun"
expect(earth.numberFromSun).toEqual(3)
it "is the densest of all the planets"
expect(earth.density).toBeGreaterThan(5.51)
Example test code written in JS using jasmine: ANS✔✔ var earth = {
isRound: true,
numberFromSun: 3,
density: 5.51
};
describe("Earth", function() {
it("is round", function() {
expect(earth.isRound).toEqual(true);
});
, Solution 2024/2025
Pepper
it("is the third planet from the sun", function() {
expect(earth.numberFromSun).toEqual(3);
});
it("is the densest of all the planets", function() {
expect(earth.density).toBeGreaterThan(5.5);
});
});
Note the syntax here: both describe and it take a string as their first
parameter, and a callback as the second. The callback to a describe
typically consists of several it functions. Inside of each it function is where
we write our expectations.
Running tests in the browser ANS✔✔ setup:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Our First Jasmine Tests</title>
<link
href="https://cdnjs.cloudflare.com/ajax/libs/jasmine/3.0.0/jasmine.css"
rel="stylesheet" />
</head>
<body>
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