Do not underestimate the power of a decorator function

Question

Do not underestimate the power of a decorator function

I need help writing tests for the following code using jest:

    @Debounce(100)
    private checkDataToPositionInStep(): void {
        
        const proposalConsultData = this.proposalConsultResponseStore.get();

        if(proposalConsultData?.documentProposalData?.length > 1) {
            this.fullScreenLoaderService.hideLoader();
            this.router.navigate(['proposta-enviada']);
            return;
        }

        if(proposalConsultData?.warrantyData?.plateUf) {
            this.fullScreenLoaderService.hideLoader();
            this.router.navigate(['upload']);
        }

        if(proposalConsultData?.bankData?.branchCode) {
            this.fullScreenLoaderService.hideLoader();
            this.scrollService.next(STEP_ACCORDION.DADOS_GARANTIA.STEP);
            this.stepperService.next(STEP_ACCORDION.DADOS_GARANTIA.ID);
            return;
        }
        
        this.fullScreenLoaderService.hideLoader();
        this.scrollService.next(STEP_ACCORDION.DADOS_BANCARIOS.STEP);
        this.stepperService.next(STEP_ACCORDION.DADOS_BANCARIOS.ID);
        return;
    }

The debounce decorator used is defined as follows:

export function Debounce(timeout: number): Function {
    return function (target, propertyKey: string, descriptor: PropertyDescriptor) {
        const original = descriptor.value;
        descriptor.value = function debounce(...args) {
            setTimeout(() => {
                original.apply(this, args);
            }, timeout);
        }
        return descriptor;
    }
}

When running npm run:coverage, all lines below decorators are not being covered. Is there a way to cover these lines?

I attempted to test the checkDataToPositionInStep method like this:

it('Should call checkDataToPositionInStep with only bankData', () => {
    const proposalConsultMock = <any> {
      bankData: {
        branchCode: '01901'
      }
    };
    (facade as any).checkDataToPositionInStep(proposalConsultMock );
  });

I expected jest to cover the checkDataToPositionInStep method.

javascript angular typescript jestjs code-coverage

Answer 1

Answer №1

Firstly: Have you remembered to include an expect(...) call? For example:

    expect(
      (facade as any).checkDataToPositionInStep(proposalConsultMock)
    ).not.toThrowError();

Second point: It's important to test your decorators separately from your main components. This way, you can ensure that both the checkDataToPositionInStep function and the returned function from Debounce are properly tested in separate test files:

it('should perform a specific action', () => {
    // Create an instance
    const debounceFunction = Debounce(60);

    // Call the function
    const result = debounceFunction(params...);

    // Verify the expected outcome
    expect(result).toBe(something);
  });

Also, make sure that your test file is correctly included in the coverage configuration.

Lastly, I have a different perspective than @facundo regarding test coverage importance. It ultimately depends on the situation, but for reasons related to code quality, it's advisable to aim for a certain level of code testing to prevent software regressions.

Answer 2

Firstly: Have you remembered to include an expect(...) call? For example:

    expect(
      (facade as any).checkDataToPositionInStep(proposalConsultMock)
    ).not.toThrowError();

Second point: It's important to test your decorators separately from your main components. This way, you can ensure that both the checkDataToPositionInStep function and the returned function from Debounce are properly tested in separate test files:

it('should perform a specific action', () => {
    // Create an instance
    const debounceFunction = Debounce(60);

    // Call the function
    const result = debounceFunction(params...);

    // Verify the expected outcome
    expect(result).toBe(something);
  });

Also, make sure that your test file is correctly included in the coverage configuration.

Lastly, I have a different perspective than @facundo regarding test coverage importance. It ultimately depends on the situation, but for reasons related to code quality, it's advisable to aim for a certain level of code testing to prevent software regressions.

Answer 3

Answer №2

Appreciate the assistance, everyone! I was able to solve the issue by utilizing jest.useFakeTimers() and jest.runAllTimers();. The setTimeout function was causing the problem. The snippet below now successfully handles the checkDataToPositionInStep method.

 proposalConsultMock = <any> {
  documentProposalData: [{
    tpDocumentoProposta: 149
},{
    tpDocumentoProposta: 90
  }],
};

jest.useFakeTimers();
setTimeout(() => {
  (facade as any).checkDataToPositionInStep(proposalConsultMock);
}, 1000);
jest.runAllTimers();

Answer 4

Appreciate the assistance, everyone! I was able to solve the issue by utilizing jest.useFakeTimers() and jest.runAllTimers();. The setTimeout function was causing the problem. The snippet below now successfully handles the checkDataToPositionInStep method.

 proposalConsultMock = <any> {
  documentProposalData: [{
    tpDocumentoProposta: 149
},{
    tpDocumentoProposta: 90
  }],
};

jest.useFakeTimers();
setTimeout(() => {
  (facade as any).checkDataToPositionInStep(proposalConsultMock);
}, 1000);
jest.runAllTimers();

Answer 5

Answer №3

Here's a piece of friendly advice - instead of focusing solely on coverage numbers, prioritize ensuring that your code is thoroughly tested. To make sure that the Debounce decorator is well-tested, consider creating a dedicated set of unit tests for it.

UPDATE

I'd like to clarify my statement about not worrying too much about coverage itself. While code coverage is an essential metric to monitor, remember that high coverage doesn't necessarily mean comprehensive testing. It's important to test everything thoroughly.

import { Debounce } from './Debouncefile';

describe('Debounce', () => {
  it('should perform as expected', () => {
    // Arrange
    const debounceFunction = Debounce(60);

    // Act
    const result = debounceFunction(params...);

    // Assert
    expect(result).toBe(something);
  });
});

Answer 6

Here's a piece of friendly advice - instead of focusing solely on coverage numbers, prioritize ensuring that your code is thoroughly tested. To make sure that the Debounce decorator is well-tested, consider creating a dedicated set of unit tests for it.

UPDATE

I'd like to clarify my statement about not worrying too much about coverage itself. While code coverage is an essential metric to monitor, remember that high coverage doesn't necessarily mean comprehensive testing. It's important to test everything thoroughly.

import { Debounce } from './Debouncefile';

describe('Debounce', () => {
  it('should perform as expected', () => {
    // Arrange
    const debounceFunction = Debounce(60);

    // Act
    const result = debounceFunction(params...);

    // Assert
    expect(result).toBe(something);
  });
});

Do not underestimate the power of a decorator function

Answer №1

Answer №2

Answer №3

UPDATE

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