In Xcode go into the Scheme for Testing (top of screen) or Option Command U.  On the Test pane the Info tab has a check box for the Debugger.  Uncheck it and testing will not spin-up a Debug Executable which will save lots of time while running test.   And if you are doing TDD - you never use the old Debugger anyway. - right!

Here's my autocomplete code snippet for writing a unitTest.  I  like that  it contains  working example code in the Given/When/Then format.

    func test_<#MethodName#>_<#Scenario#>() throws {

        // a really great explaination for future you

        // Given conditions

        var someValue = false

        // When some action occurs

        if  !someValue  { someValue.toggle() }

        // Then test this

        XCTAssertTrue( someValue )

    }

I sometimes forget the format of a simple TDD test - so I have a code complete snippet for an example.  This one uses the classic - Given/When/Then pattern.

Boy - this was hard to figure out.  But I found it buried in a StackExchange post...

I have a SwiftUI Toggle button on my App's Setting page.  It controls the printing of an Arabic numeral-style equation on the History page of the App.

At the App launch, it is Off.  But after the app has run through a few UI Tests - it could be in any state.  Tests need a reliable state to function appropriately.

One of the secrets is to use firstMatch on the Toggle - I think this means the switch is a child of the Label and we expect there is only ONE child (hence firstMatch):

 base10Toggle.switches.firstMatch.tap()

Then I used the practice of returning the toggle to OFF after the test.  To ensure the next test will find the state consistant.

Figuring  out how to create  your own autocomplete  code snippets in  Xcode is  tough.   The  snippet browser  doesn't have  a button (like it should).  I have to google it  each time.   

The menu item is in the last place you will look:   Editor > Create Code Snippet...

Then you will want to know how to encode placeholder text.  That secret is with  <#  placeholder text #>.

Good  luck.