Ways to boost branch coverage in Jest when working with a for-in loop that has an if statement

Question

Ways to boost branch coverage in Jest when working with a for-in loop that has an if statement

Here is a piece of code that maps specific fields from one object to another and copies their values:

//Function parameters
var source = {"f1": "v1", "f2": "v2", "f3":"v3"};
var fieldsMapping = {"f1": "c1", "f2":"c2"};

//Function definition begins
var copiedObj = {};    
for (var name in source) {
  if (source.hasOwnProperty(name)) { //Line X
    if(fieldsMapping[name]){
        copiedObj[fieldsMapping[name]] = source[name];
    }
  }
}

console.log(copiedObj); //outputs {c1: "v1", c2: "v2"}

I have created a test case for this function using jest, achieving 100% line coverage. However, branch coverage indicates that Line X is not covered. According to standards such as those found in SonarSource and TSLint, a for-in loop should be accompanied by an if condition.

Can anyone provide suggestions on how to create a test case that improves branch coverage for this scenario?

javascript typescript unit-testing jestjs tslint

Answer 1

Answer №1

Implementing an extra if statement in your code adds a layer of robustness to handle unexpected situations. These checks are crucial for ensuring the stability and reliability of your code, even though they may not be directly testable. Similar scenarios can occur in other parts of your code, such as adding default cases in switch statements or using assertion statements with hidden else branches.

Although removing these robustness measures and assertions may seem tempting, they play a vital role in identifying potential side effects of future changes. It is important to carefully analyze your coverage report to determine which aspects of your code require thorough testing.

Furthermore, it's essential to remember that achieving high code coverage does not necessarily equate to having a high-quality test suite. A quality test suite should be able to uncover likely bugs within the code, regardless of the overall coverage percentage. Simply having 100% coverage does not guarantee that all potential issues will be detected.

Answer 2

Implementing an extra if statement in your code adds a layer of robustness to handle unexpected situations. These checks are crucial for ensuring the stability and reliability of your code, even though they may not be directly testable. Similar scenarios can occur in other parts of your code, such as adding default cases in switch statements or using assertion statements with hidden else branches.

Although removing these robustness measures and assertions may seem tempting, they play a vital role in identifying potential side effects of future changes. It is important to carefully analyze your coverage report to determine which aspects of your code require thorough testing.

Furthermore, it's essential to remember that achieving high code coverage does not necessarily equate to having a high-quality test suite. A quality test suite should be able to uncover likely bugs within the code, regardless of the overall coverage percentage. Simply having 100% coverage does not guarantee that all potential issues will be detected.

Answer 3

Answer №2

It is important to note that in order to achieve 100% branch coverage, the if statement must not be executed for certain specific test cases, unlike line coverage which shows 100% when the if is executed for all test cases.

One way to ensure the if statement is not executed for certain cases is by utilizing the behavior of hasOwnProperty, as it returns false for properties inherited from the prototype:

const base = { a: 1};
const source = Object.create(base, {b: 2, c: 3} );
const fieldsMapping = {a: 'aa', b: 'bb', c: 'cc'};

expect(yourFunction(source, fieldsMapping)).toEqual({ bb: 2, cc: 3 });

Remember, it's good practice to not become obsessed with reaching a 100% coverage goal.

Answer 4

It is important to note that in order to achieve 100% branch coverage, the if statement must not be executed for certain specific test cases, unlike line coverage which shows 100% when the if is executed for all test cases.

One way to ensure the if statement is not executed for certain cases is by utilizing the behavior of hasOwnProperty, as it returns false for properties inherited from the prototype:

const base = { a: 1};
const source = Object.create(base, {b: 2, c: 3} );
const fieldsMapping = {a: 'aa', b: 'bb', c: 'cc'};

expect(yourFunction(source, fieldsMapping)).toEqual({ bb: 2, cc: 3 });

Remember, it's good practice to not become obsessed with reaching a 100% coverage goal.

Ways to boost branch coverage in Jest when working with a for-in loop that has an if statement

Answer №1

Answer №2

Similar questions

Attempting to sort through an array by leveraging VueJS and displaying solely the outcomes

The behavior of Datatables varies depending on the screen resolution

Tips for validating form data in JavaScript before invoking a PHP file

Need assistance as require function is not functioning as anticipated

Yii - The jQuery.fn.yiiGridView function is causing an error of undefined when attempting to use the update() function

How can I verify if there are duplicate items in the cart using Angular 5?

Validate a JSON object key

"Doubling Up: The Art of Adding Elements to a Polymer

Learn how to dynamically populate text fields with data when an option is selected from a dropdown menu that is populated from a database using Laravel and Ajax technologies

Eradicating a character from an Object using Jquery/Javascript

Using Vuejs to dynamically apply a class and trigger a function based on a specified condition

Looking to add a JSON object to the Angular.JS controller's scope

What is the best way to retrieve and display the heading of the current section that is being viewed using Bootstrap Vue's ScrollSpy feature?

Techniques for removing invalid characters from a JSON $http.get() request

Are sporadic ajax issues going unnoticed?

The connectivity feature in aframe's dynamic rooms is currently experiencing compatibility issues with the EasyRTC

What is the best way to ensure a function waits for a stable database connection before proceeding?

Converting an array of objects to an array of JSON objects in TypeScript

Creating a Geometric Shape using Three.js

Scrape data from websites where the main URL remains constant but the information in the table varies