Jest basic

Setup Jest: Getting started Jest with Typescript

toBe() vs toEqual()

toBe compares strict equality, using ===.
toEqual compares the values of two variables. If it’s an object or array, it checks the equality of all the properties or elements.

Run only the test group

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describe.only("addition test", () => {
    it("add 1 + 1 to be 2", () => {
      expect(1 + 1).toBe(2);
    });
});

Skip the test group

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describe.skip("addition test", () => {
    it("add 1 + 1 to be 2", () => {
      expect(1 + 1).toBe(2);
    });
});

Loop tests with multiple test cases

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describe("Addition test", () => {
    [
        { a: 1, b: 2, c: 3 },
        { a: 2, b: 4, c: 6 }
    ].forEach(testcase => {
      it(`addition: ${testcase.a} + ${testcase.b} to be ${testcase.c}`, () => {
        expect(testcase.a + testcase.b).toBe(testcase.c);
      });
    });
});

Run only fit tests

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fit("add 1 + 1 to be 2", () => {
  expect(1 + 1).toBe(2);
});

Skip only xit tests

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xit("add 1 + 1 to be 2", () => {
  expect(1 + 1).toBe(2);
});

References