@aegis-techno/ngx-testing-tools

NgxTestingTools

This library is a helper that encourages leaner, meaner specs.

It provide Given When Then Concepts and mock tool for Jest and Angular

Running unit tests

Run ng test ngx-testing-tools to execute the unit tests via jest.

Given When Then Concepts

This library is a helper that encourages leaner, meaner specs using Given, When, and Then.

The basic idea behind this is a humble acknowledgement of given-when-then as the best English language analogue we have to arrange-act-assert

Prior Art + Credit

The concept (and implementation) is based on the work of HiRez.io, who've done an amazing implementation of the original jasmine-given library by Justin Searls, which is in turn based on rspec-given by Jim Weirich.

Example

describe('A context', () => {
    let fakeNumber: number;
    let actualResult: any;

    function addTwo(num: number) {
        return num + 2;
    }

    Given(() => {
        fakeNumber = undefined;
        actualResult = undefined;
    });

    describe('should run "Given" before "When" and "When" before "Then"', () => {
        Given(() => {
            fakeNumber = 2;
        });

        When(() => {
            actualResult = addTwo(fakeNumber);
        });

        Then(() => {
            expect(actualResult).toBe(4);
        });
    });

    describe("redundant test execution example", () => {
        context("a traditional spec with numerous Then statements", () => {
            var timesGivenWasInvoked = 0,
                timesWhenWasInvoked = 0;
            Given(() => {
                timesGivenWasInvoked++;
            });
            When(() => {
                timesWhenWasInvoked++;
            });
            Then(() => expect(timesGivenWasInvoked).toBe(1));
            Then(() => expect(timesWhenWasInvoked).toBe(2));
            Then(() => expect(timesGivenWasInvoked).toBe(3));
            Then(() => expect(timesWhenWasInvoked).toBe(4));
        });


        context("a spec with one Then and multiple And statements", () => {
            var timesGivenWasInvoked = 0,
                timesWhenWasInvoked = 0;
            Given(() => {
                timesGivenWasInvoked++;
            });
            When(() => {
                timesWhenWasInvoked++;
            });
            Then(() => expect(timesGivenWasInvoked).toBe(1));
            And(() => expect(timesWhenWasInvoked).toBe(1));
            And(() => expect(timesGivenWasInvoked).toBe(1));
            And(() => expect(timesWhenWasInvoked).toBe(1));
            Then(() => expect(timesWhenWasInvoked).toBe(2));
        });
    });

Given

The Given section specifies a starting point, a set of preconditions that must be true before the code under test is allowed to be run. In standard test frameworks the preconditions are established with a combination of setup methods

When

The When clause specifies the code to be tested ... oops, excuse me ... specified. After the preconditions in the given section are met, the when code block is run.

Then / ThenExpect

The Then clauses are the postconditions of the specification. These then conditions must be true after the code under test (the When clause) is run.

And

The And clauses are play after the Then clause find before. The And clauses don't support "random order running test".

Mock

Utils method :

• configureTestBed(moduleDef?: TestModuleMetadata), for the configuration of the TestBed in a Given.
• createTestContext(component: Type<T>), for create un wrapper of a fixture for the component class given.
• provideSpyObjForClass, create a SpyObj.
• injectMock(classType: Type<T> | AbstractType<T>), for retreive a mock.

Usage

describe('MyComponent', () => {
    let testContext: TestContext<MyComponent>;

    configureTestBed({
            providers: [
                provideSpyObjForClass(MyService)
            ]
        },
    );

    Given(() => {
        injectMock(MyService).foo.and.returnValue(["TEST"]);
    })

    When(async () => {
        testContext = createTestContext(MyComponent);
        await testContext.whenStable();
    });

    Then('should be created', () => {
        expect(testContext.component).toBeTruthy();
    });

    Then('should have retrieve data from service', () => {
        expect(testContext.component.bar).toBe("TEST");
    });
});