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Testing Tips

This article is about performing tests on your Swift application. It will be updated from time to time.

Testing frameworks

Xcode has two frameworks to perform tests:

  • XCTest: perform unit tests and integration tests on your business code.
  • XCUITest: perform integration tests on your graphical interface.

To fully test an application you should use both.

XCTest consideration

For the SolvoKu application project I need to perform many test on the algorithms used to generate and solve sudoku grids.

To write those tests I had to find some way to fastly write initialization of objects. I found two ways doing so, both are based on writing a string representation of an object.

Building an object from a string representation

First thing I did was to both:

  • write a function to representant a sudoku grid as a string
  • write a function to build a sudoku grid from a string representation

This string representation allow me to represents both values and candidates in the grid.

Building an object from a string representation, second version

The second way I use is to implement the CustomStringConvertible protocol to retrieve a description representing the call to perform to construct an object. Can be used only on a class where properties are immutable after initialization, or on structures.

    class AClass: CustomStringConvertible {
    let prop1: Int

    init(prop1: Int) {
            self.prop1 = prop1

        var description: String {
            return "AClass(prop1: \(prop1))"

After manually testing a piece of code I can use this to fastly build a series of tests to ensure non-regression. I use this technique not to build entry parameters, but to check results of my algorithms.