func testSum2NumbersResult() {
    // This is an example of a functional test case.
    // Use XCTAssert and related functions to verify your tests produce the correct results.
    let sum = viewController.sum2Numbers(num1: 1, num2: 2)
    XCTAssertEqual(sum, 3, "Sum of 1 and 2 is not equal 3")
}