Unit Testing 04. Math Enforcer nested describe My solution

describe("mathEnforcer", () => {
    describe("addFive", () => {
        it("not number", () => {
            expect(mathEnforcer.addFive('softuni')).to.equal(undefined);
        });
        it("positive", () => {
            expect(mathEnforcer.addFive(5)).to.equal(10);
        });
        it("negative", () => {
            expect(mathEnforcer.addFive(-2)).to.equal(3);
        });
        it("floating-point", () => {
            expect(mathEnforcer.addFive(1.1)).to.be.closeTo(6.1, 0.01);
        });
    });

    describe("subtractTen", () => {
        it("not number", () => {
            expect(mathEnforcer.subtractTen('softuni')).to.equal(undefined);
        });
        it("positive", () => {
            expect(mathEnforcer.subtractTen(15)).to.equal(5);
        });
        it("negative", () => {
            expect(mathEnforcer.subtractTen(-2)).to.equal(-12);
        });
        it("floating-point", () => {
            expect(mathEnforcer.subtractTen(1.5)).to.be.closeTo(-8.5, 0.01);
        });
    });

    describe("sum", () => {
        it("sum1 number, sum2 not number => undefined", () => {
            expect(mathEnforcer.sum(3, 'yabloko')).to.equal(undefined);
        });
        it("sum1 not number, sum2 number => undefined", () => {
            expect(mathEnforcer.sum('yabloko', 10)).to.equal(undefined);
        });
        it("sum1 not number, sum2 number => undefined", () => {
            expect(mathEnforcer.sum('yabloko', 'grusha')).to.equal(undefined);
        });
        it("sum1  number, sum2 number => 15", () => {
            expect(mathEnforcer.sum(5, 10)).to.equal(15);
        });
        it("sum1  number, sum2 number negative", () => {
            expect(mathEnforcer.sum(-5, -10)).to.equal(-15);
        });
        it("sum1  number, sum2 number negative", () => {
            expect(mathEnforcer.sum(3.14, 5.18)).to.equal(8.32);
        });
    });
});