In the Apple ecosystem I'm guessing your using XCode - so you have easy access to a Unit Testing Framework XCTest.  It's been around since version 5 of XCode ... that is a while back... maybe I'll look that up some time...  (2013).

Like all of Apple's documentation - it's very very sparse.  Here is the Overview:

"Use the XCTest framework to write unit tests for your Xcode projects that integrate seamlessly with Xcode's testing workflow.

Tests assert that certain conditions are satisfied during code execution, and record test failures (with optional messages) if those conditions aren’t satisfied. Tests can also measure the performance of blocks of code to check for performance regressions, and can interact with an application's UI to validate user interaction flows."

There is nothing earth shattering about that - unless you've been unit testing and coding for some time and then the word that should catch you attention is "performance" - WHAT!  XCTest is also a performance testbed... and it's very easy to use.

Apple Developer Documentation - XCTest

Notes on XCTest Usage:

Much like any xUnit framework ... one extends the XCTestCase with a new TestCase class and inside the class write multiple test methods (beginning with the word "test") and the framework will pick up this convention - it's a nice integration touch - thanks Apple!

The Apple class XCTAssert family of functions is used to check for Boolean conditions, nil or non-nil values, expected values, and thrown errors.

UI Test - or what I've always called Story Test are defined using User Interface Tests and the Performance Tests are also easy to use.

A great tutorial - with step by step guidance on setting up the XCTesting framework and XCode is found in Project 39 of Hacking with Swift.

Making a Unit Test Run Fast on validation of a View -> ViewInspector

This is an alternative to the Swift - XCode UI Test framework that has to run the App to drive the inspection and all the UI - which takes a lot of time (if your a computer). 

Let's try to install https://github.com/nalexn/ViewInspector via Swift Package Manager.  A nice testing utility for SwiftUI by Alexey Naumov (nalexn).  His blog article about View Inspector - Who said we cannot unit test SwiftUI Views?

In Xcode select File ⭢ Swift Packages ⭢ Add Package Dependency... Copy-paste repository URL: https://github.com/nalexn/ViewInspector Hit Next two times, under Add to Target select your test target. There is no need to add it to the build target. Hit Finish

Go into Project Build Setting - search for ENABLE_TESTING_SEARCH_PATHS and set to YES

Learn to use the Inspector:  https://github.com/nalexn/ViewInspector/blob/master/guide.md

There are 4 steps to configuring your XCTest Class file:

1. Add import ViewInspector

2. Extend your view to conform to Inspectable in the test target scope.

3. Annotate the test function with throws keyword to not mess with the bulky do { } catch { }. Test fails automatically upon exception.

4. Start the inspection with .inspect() function

Look thru the Guide.md for examples - don't do what I did and skip ahead... go slow and test that the framework is installed and functioning properly - an important lesson to learn when practicing TDD.