Jasmine context + Typescript

Question

I'm using Jasmine with Typescript and recently we started using the this context in beforeEach and it.

Example:

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

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

The problem is that TypeScript is not smart enough to figure out that this inside beforeEach is exactly the same this as in it. Does anyone know an easy way to 'hint' typescript about this fact?

Is this even possible?

Answer 1

You can typehint this in functions. Actually, if you only use arrow functions (in describe, beforeEach and it), the context this will be the outermost global context, I suppose. Since that one cannot be annotated, I suggest passing a regular old-style function to the outermost describe:

// Dummy-type Jasmine functions (only for this MWE)
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('Test suite', function (this: TestSuiteContext) {
    beforeEach(() => {
        this.myObj = new A();
    });

    it('should do something', () => {
        const message: string = this.myObj.aProperty;
    });
});