can we check the validation of uitextfield while Unit Testing?

Question

Suppose we have some validation in our ViewController ( say vc1 ) for a UItextfield in shouldChangeCharactersInRange method, as user only can enter the numbers not the alphabets or other special character.

I just want to know that in our XCTestCase class, is this possible in unit testing, to check for a particular uitextfield, is allowing some characters (in my case only numbers) or not?

Answer 1

Make unit tests that call shouldChangeCharactersInRange and check the expectation that the result should be true, or false.

This is an example of how to unit test delegate methods. Where UIKit invokes a particular method, just have tests call the same thing.

Even though a particular class may implement the delegate method, it's better if the test remains ignorant of this. UIKit asks the text field for its delegate, then calls it. Our tests should do the same, and invoke through the delegate. Otherwise we are locking down the implementation, which would make it harder to refactor the delegate methods.

func testMyTextField_ShouldAllowAlphabeticCharacters() {
    let vc = // …Whatever you do to load your view controller
    vc.loadViewIfNeeded() // Make sure text field is loaded
    let field = vc.myTextField

    // Call through field.delegate, not through vc
    let result = field.delegate.textField(field,
                         shouldChangeCharactersIn: NSMakeRange(0, 1),
                         replacementString: "a")

    XCTAssertTrue(result)
}