Unit Testing in Angular(7/8/9) Using Jasmine and Karma Part-2

Welcome to the second installment of unit testing in Angular application. In this blog, you will learn the remaining things about unit testing in Angular application and how to write unit tests for different scenarios.

Before we start unit tests if you have missed the part-1, then you can check it here.

So, let’s get started.

Table of Contents to be covered:

1. How to write test cases to check comparison for the numbers
2. How to write test cases for EventEmitter
3. How to run a single test case
4. How to run a single spec file
5. How to skip a single test case
6. How to skip a single spec file
7. How to run the test cases in Firefox
8. Reference link

Let’s start with how to write the test cases for the different scenarios for the component.

(1) How to Write Test Cases to Check Comparison for the Numbers.

1. How to check if the value of a variable is a number or not?

Let’s say we have a variable in a TS file like.

public toBeNaN = 0 / 0;

If you want to check that toBeNaN should not be a number, then first, you need to access in the spec file, and then you need to use the method which is provided by jasmine.

 it('toBeNaN variable should not be a number.', () => {
   var toBeNaNValue = component.toBeNaN;
   expect(toBeNaNValue).toBeNaN();
 });

The above test cases will check the value of the toBeNaN variable should not be a number, and if the value is not a number, then it will run successfully, or else the above test case will be false.

2. How to check that array contains the desired value or not.

Let’s say we have a method in a TS file that returns an array with some value.

 arrayList() {
   return ['first name','last name', 'middle name'];
 }

In order to check whether the array contains the first name or not, then we can check something like,

 it("Should contain 'first name' in an array which return by ArrayList method.", () => {
   const name = component.arrayList();
   expect(name).toContain('first name');
 });

So as per the above test case code first, it will call the ArrayList method and store the value in name const, and then it will check that name contain ‘first name’ or not if it has then test case will be a success and if not then it will be a failure.

3. How to check that array value should be equal.

Let’s tale the above example, and in that, we return the value in an array something like: [‘first name,’ ‘last name,’ ‘middle name’];

Then if we want to check that the return array should be the same or equal to the above array value, then we need to write the test case something like.

it("arrayList method return array value Should equal to mockArray value.", () => {
   const name = component.arrayList();
   const mockArray = ['first name','last name', 'middle name'];
   expect(name).toEqual(mockArray);
 });

Note: – The above solution will match the same array with value on a particular index as well.

4. How to check that variable value is less than or not.

Let’s say we have a variable in TS file, and if we want to check that, it should be less than 10.

public toBeLessThanValue: number = 1.5;

 it('Value of toBeLessThanValue variable should be less than 10.', () => {
   const percent = component.toBeLessThanValue;
   expect(percent).toBeLessThan(10);
 });

So in order to check that the value of the variable should be less than 10, we need to use the toBeLessThan method, which is provided by jasmine.

Note:- We can also simplify the above solution as I first store the value of the variable is a constant, instead of that, we can directly use that variable, something like the solution below.

it('Value of toBeLessThanValue variable should be less than 10.', () => {
   expect(component.toBeLessThanValue).toBeLessThan(10);
 });

For your practice, you can use the below method and write your own test cases.

1. toBeLessThanOrEqual()
2. tobe greater than()
3. toBeGreaterThanOrEqual()

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(2) How to write test cases for event emitter.

1. How to write test cases for EventEmitter.

Let’s say we have an EventEmitter in the TS file, and also we have a method emitToParent, and while calling this method, it should emit the value ‘true.’

So step 1, we should have an @output EventEmitter variable, and we should have a method for emitting the value. Here we have the emitToParent method.

@Output() data = new EventEmitter();

 emitToParent() {
   this.data.emit(true);
 }

So to write test cases for Event Emitter, we need to write case something like below.

it('Should emit the value once emitToParent method calling.', () => {
   spyOn(component.data, 'emit');
   component.emitToParent();
   expect(component.data.emit).toHaveBeenCalledWith(true);
 });

So using the toHaveBeenCalledWIth method, we can check that emit is successful or not.

(3) How to run a single test case.

If we want to run a single test case, then we need to add ‘f’ as a prefix in that test cases so it will become fit something like.

it('should not be null isLoggedInArrary', () => {
   const isLoggedInArrary = component.isLoggedInArrary;
   expect(isLoggedInArrary).toEqual(['a']);
 });
 
 fit('close should emit the value once emitToParent method calling.', () => {
   spyOn(component.data, 'emit');
   component.emitToParent();
   expect(component.data.emit).toHaveBeenCalledWith(true);
 });

In the above case, it will only run the second test case as we provided f as a prefix to that test case no matter if other test cases are gonna be a success or fail.

(4) How to run a single spec file.

If we want to run a single test spec file, then we need to add ‘f’ as a prefix in that spec file describe method so it will become fdescribe something like…

fdescribe('HomeComponent', () => {
 let component: HomeComponent;
 let fixture: ComponentFixture;
 
 beforeEach(async(() => {
   TestBed.configureTestingModule({
     declarations: [HomeComponent]
   })
     .compileComponents();
 }));

(5) How to skip a single test case

If we want to skip a single test case, then we need to add ‘X’ as a prefix in that test cases so it will become fit something like,

 it('should not be null isLoggedInArrary', () => {
   const isLoggedInArrary = component.isLoggedInArrary;
   expect(isLoggedInArrary).toEqual(['a']);
 });
 
 xit('close should emit the value once emitToParent method calling.', () => {
   spyOn(component.data, 'emit');
   component.emitToParent();
   expect(component.data.emit).toHaveBeenCalledWith(true);
 });

In the above case, it will only skip the second test case as we provided X as a prefix to that test case no matter if that test case is gonna be a success or fail.

(6) How to skip a single spec file.

If we want to skip a single test spec file, then we need to add ‘X’ as a prefix in that spec file describe method so it will become xdescribe something like.

xdescribe('HomeComponent', () => {
 let component: HomeComponent;
 let fixture: ComponentFixture;
 
 beforeEach(async(() => {
   TestBed.configureTestingModule({
     declarations: [HomeComponent]
   })
     .compileComponents();
 }));

So in the above case, xdescribe will not run the test case; it will run another spec file.

(7) How to run the test cases in Firefox.

So as we learn in Test cases in Angular part-1, while we run the test cases in Angular using ng test, then it will automatically open the chrome browser, but what if we want to run the test cases in Firefox.

That is also possible to run the test cases in Firefox, and for that first, you should have Firefox on your laptop or desktop. Then you need to install one package and need to set the configuration to run the test cases in Firefox.

Step 1: install node package karma-firefox-launcher using the terminal by below command

Command: npm install karma-firefox-launcher –save-dev

"karma-firefox-launcher": "^1.2.0",

Step 2: Then go to the karma.conf.js file and add plugins like using the below line after require(‘karma-chrome-launcher’), line.

require('karma-firefox-launcher'),

Step 3: Then add Firefox in browsers array something like below.

browsers: ['Chrome', 'Firefox'],

Step 4: Run the test case using the ng test, and it will open both the browser as shown in the below video.

Firefox Test case: https://drive.google.com/file/d/1DKluBomf8g6srN76HSg3bu9v-p_a520N/view?usp=sharing

(8) Reference link

Github: https://github.com/parthsardhara/Angular-Test-Cases

Wrapping Up:

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