CODEWITHSUNDEEP
typescript
Jessica M.
Jessica M.

Reputation: 1

How to call a static method of class?

I am currently working on an Angular4 Web application and I am trying to write a unit test for a class and pipes that have only public static methods. By now I have not found any solution to do that. Anything that works for components, service etc. does not work here.

Example: Class

export class StringExtensions {
    public static firstToLowerCase = ( argument: string ): string => {
        return `${ argument.substr( 0, 1 ).toLowerCase() }${ argument.substr( 1 ) }`;
    }
}

Example: not working Unittest

import {StringExtensions} from './string-extensions';

describe('StringExtensions', () => {

    let classStringExtensions: StringExtensions;
    const argument: string = 'ArgumenTas';

    beforeEach(() => {
        classStringExtensions = new StringExtensions();
    });

    afterEach(() => {
        classStringExtensions = null;
    });

    it('should ...', () => {
        expect(classStringExtensions.firstToLowerCase(argument)).toBe('argumenTas');
    });

});

ErrorMessage:

ERROR in .../string-extensions.spec.ts (17,38): 
Property 'firstToLowerCase' does not exist on type 'StringExtensions'.

Upvotes: 0

Views: 674

Answers (1)

Igor
Igor

Reputation: 62298

It is because you calling the static method on an instance, you need to call it on the type as static members are accessed at the type level.

expect(StringExtensions.firstToLowerCase(argument)).toBe('argumenTas');

The current code inside of the beforeEach and afterEach are also not necessary.

This question is general to typescript and not specific to any framework.

Upvotes: 1

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