Best way to test drive in a non-nullable field

you are trying to add a non-nullable field foreign key
provide a one-off default now (will be set on all existing rows with a null value for this column)
django nullable field
django model fields
not null constraint failed
no such column django
no migrations to apply
django makemigrations no changes detected

I have a kotlin object like so;

data class Car(
    val id: UUID

the id is not nullable thanks to kotlin compile time checks. I just want to make sure that in the future, a test will fail if anyone changes the line to

   val id: UUID?

because that field being nullable will mess up several services that depend on id (save/get/etc). I was thinking i could make another Car-like class with a nullable id, and write tests for my services to make sure they will handle null ids, but its not super easy, and it seems wrong.

My other option seems to be accessing an instance method of the id in test, like so

fun `dont change to nullable`(){
   Car().id.timestamp() // calling timestamp() will no longer compile if someone changes UUID to UUID?

but this seems confusing

I look at tests as though they protect the code. So if anyone comes in they should be able to change anything they want, and as long as they dont break any existing tests, they can be confident that they didnt break any existing functionality. But i dont know how to stop someone from changing "UUID" to "UUID?", which would introduce a huge bug

If you are ok with using reflection, then you could do this:


You are trying to add a non-nullable field 'form_ptr , "You are trying to add a non-nullable field 'form_ptr' to aboutpage without a How do I change my `AboutPage` class to avoid this message? Here’s how to make the most of your test drive: Take a passenger to find out how the car feels to them. Allow at least an hour for your test drive – in town, out on the open road and on a motorway if possible. If you’re on a motorway or dual carriageway, try overtaking – checking for good acceleration and any blind spots.

To make sure that the constructor or method parameter doesn't have a nullable type, you should pass null to this method and check if it throws IllegalArgumentException. You can do it in 2 ways:

  1. Call it from Java: new Car(null);
  2. Call it from Kotlin and pass a variable of a platform type Car(getNull())

getNull() should be defined in Java:

public static <T> T getNull() {
    return null;

(makemigrations requires default when adding non-nullable field , How do I change my `AboutPage` class to avoid this message? My goal is to make a page that where I can put a form with descriptions and other  If you want to assign a value of a nullable value type to a non-nullable value type variable, you might need to specify the value to be assigned in place of null. Use the null-coalescing operator ?? to do that (you can also use the Nullable<T>.GetValueOrDefault(T) method for the same purpose):

This is probably good enough:

data class Car(
    // NOTE: Absolutely don't change this to 'UUID?' !!
    val id: UUID

The people who ignore that comment are the same people that will simply remove or uncomment any automated test you wrote to uphold such a rule.

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PC Mag, python makemigrations You are trying to add a non-nullable field 'bar' to foo deconstruct of field is not the right place, I described in PR why) On testing this, I found a case where the generated migration results in a crash; see  A nullable type has the same assignment rules as a value type. It must be assigned a value before using it if nullable types are declared in a function as local variables. If it is a field of any class then it will have a null value by default. For example, the following nullable of int type is declared and used without assigning any value.

Professional Visual Studio 2010, Watcom SQL was not a top performer on any of our tests, so much of its The test modifies the value of a nonindexed field so that only the row has to be updated. We ran this test in much the same way we ran the Random Read test, taking change the attribute of one of the table columns from NULLable to NOT NULL. Teams. Q&A for Work. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.

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