How to use the class-validator.validateSync function in class-validator

it("should fail if isin is empty", () => {
		const errors: ValidationError[] = validateSync(myClass);

		expect(errors.length).toBe(1);
		expect(errors[0].constraints).toBeDefined();
		expect(errors[0].constraints[validatorConstraintName]).toBeDefined();
	});

it("should fail if the object to validate is not a string", () => {
		const errors: ValidationError[] = validateSync(simpleClass);

		expect(errors.length).toBe(1);
		expect(errors[0].constraints).toBeDefined();
		expect(errors[0].constraints[validatorConstraintName]).toBeDefined();
	});

public addBackend(backend: StarkBackend): void {
		if (!backend) {
			throw new Error("A backend instance must be provided");
		}

		const backendInstance: StarkBackendImpl = backend instanceof StarkBackendImpl ? backend : Deserialize(backend, StarkBackendImpl);

		StarkValidationErrorsUtil.throwOnError(validateSync(backendInstance), "The backend instance provided is not valid.");

		this.backends.set(backend.name, backend);
	}

doBeforeUpdate() {
    const errors = validateSync(this, { validationError: { target: false } });
    if (errors.length > 0) {
      throw new CustomValidationError(errors);
    }
  }
}

doBeforeUpdate() {
    const errors = validateSync(this, { validationError: { target: false } });
    if (errors.length > 0) {
      throw new CustomValidationError(errors);
    }
  }
}

doBeforeUpdate() {
    const errors = validateSync(this, { validationError: { target: false } });
    if (errors.length > 0) {
      throw new CustomValidationError(errors);
    }
  }
}

doBeforeUpdate() {
    const errors = validateSync(this, { validationError: { target: false } });
    if (errors.length > 0) {
      throw new CustomValidationError(errors);
    }
  }
}

doBeforeInsertion() {
    const errors = validateSync(this, { validationError: { target: false } });
    if (errors.length > 0) {
      throw new CustomValidationError(errors);
    }
  }

doBeforeUpdate() {
        const errors = validateSync(this, { validationError: { target: false } });
        if (errors.length > 0) {
            throw new CustomValidationError(errors)
        }
    }
}

doBeforeUpdate() {
    const errors = validateSync(this, { validationError: { target: false } });
    if (errors.length > 0) {
      throw new CustomValidationError(errors);
    }
  }