Exploring the combination of Jasmine context and Typescript

Question

Exploring the combination of Jasmine context and Typescript

Recently, while working with Jasmine and Typescript, our team has begun utilizing the this context in both the beforeEach and it functions.

For example:

beforeEach(() => {
  this.fixture = TestBed.createComponent(blablabla);
});

it('should do something', () => {
   expect(this.fixture).toBeTruthy();
});

Despite this, TypeScript seems to struggle recognizing that the this within beforeEach is the same as in it. Is there a simple way to inform TypeScript of this connection?

Is it possible to resolve this issue at all?

typescript jasmine

Answer 1

Answer №1

If you want to add type hints to functions, you can do so by using arrow functions such as typing this. Specifically, when using arrow functions within describe, beforeEach, and it, the context of this will refer to the outermost global context. Since this cannot be annotated, it is recommended to pass a traditional function to the top-level describe:

// Example Jasmine functions (for illustrative purposes)
declare const describe: (msg: string, fun: () => void) => void;
declare const it: (msg: string, fun: () => void) => void;
declare const beforeEach: (fun: () => void) => void;

class A {
    aProperty: string;
}

interface TestSuiteContext {
  myObj: A;
}

describe('Testing scenario', function(this: TestSuiteContext) {
    beforeEach(() => {
        this.myObj = new A();
    });

    it('should perform an action', () => {
        const message: string = this.myObj.aProperty;
    });
});

Answer 2

If you want to add type hints to functions, you can do so by using arrow functions such as typing this. Specifically, when using arrow functions within describe, beforeEach, and it, the context of this will refer to the outermost global context. Since this cannot be annotated, it is recommended to pass a traditional function to the top-level describe:

// Example Jasmine functions (for illustrative purposes)
declare const describe: (msg: string, fun: () => void) => void;
declare const it: (msg: string, fun: () => void) => void;
declare const beforeEach: (fun: () => void) => void;

class A {
    aProperty: string;
}

interface TestSuiteContext {
  myObj: A;
}

describe('Testing scenario', function(this: TestSuiteContext) {
    beforeEach(() => {
        this.myObj = new A();
    });

    it('should perform an action', () => {
        const message: string = this.myObj.aProperty;
    });
});

Exploring the combination of Jasmine context and Typescript

Answer №1

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