Decision Table Testing

index.test.js

function fieldIsValid({ isRequired, hasError, isEmpty }) {
  if (hasError) return false;
  if (isRequired && isEmpty) return false;
  return true;
}


describe("fieldIsValid", () => {

  describe("given it has an error", () => {
    const permutations = [
      { isRequired: true, hasError: true, isEmpty: true },
      { isRequired: true, hasError: true, isEmpty: false },
      { isRequired: false, hasError: true, isEmpty: true },
      { isRequired: false, hasError: true, isEmpty: true },
      { isRequired: false, hasError: true, isEmpty: false }
    ];

    permutations.forEach(permutation => {
      it(`should return false for values: ${JSON.stringify(permutation)}`, () => {
        const result = fieldIsValid(...permutations);
        expect(result).toEqual(false);
      });
    });

  });

  describe("given it doesn't have an error", () => {
    it("should return false if it is empty and required", () => {
      const result = fieldIsValid({ isRequired: true, hasError: false, isEmpty: true });
      expect(result).toEqual(false);
    });

    it("should return true if it is not empty and not required", () => {
      const result = fieldIsValid({ isRequired: false, hasError: false, isEmpty: false });
      expect(result).toEqual(true);
    });

    it("should return true if it is empty and not required", () => {
      const result = fieldIsValid({ isRequired: false, hasError: false, isEmpty: true });
      expect(result).toEqual(true);
    });

    it("should return true if it doesn't have errors and is required and not empty", () => {
      const result = fieldIsValid({ isRequired: true, hasError: false, isEmpty: false });
      expect(result).toEqual(true);
    });
  });

});