testing What s the best way in tests to compare nested colle

Question

testing What s the best way in tests to compare nested collections disregarding the element order e g `mapOf 1 to 2 3 ` and `mapOf 1 to 3 2 ` should compare the same

Joffrey · Answer

If order doesn t matter in the test why should it matter in production

David Kubecka · Answer

The inner list is returned from a 3rd party

ephemient · Answer

map the inner list to a set

Joffrey · Answer

gt The inner list is returned from a 3rd party So if you don t care about the order of the things returned by the third party lib you could map the list to a set at that point not in tests

David Kubecka · Answer

good point

David Kubecka · Answer

But still is there such a way to ignore the order I m not sure every situation can be solved like that slightly smiling face

David Kubecka · Answer

Also what about other advanced matchers such as ignoring property values in an instance

Joffrey · Answer

The choice of data structure is what expresses the constraints order or not unicity of elements etc in production code so I would rely on that pretty much in all situations

Joffrey · Answer

gt what about other advanced matchers such as ignoring property values in an instance That could also be expressed in production code if it doesn t matter in production by customizing equals or putting a subset of data class properties outside of the constructor If some properties use some randomness like randomly generated IDs maybe you could inject some fixed seed in tests to solve that If none of the above works you can convert both sides of the `assertEquals ` to some other representation that matches what you want to take into account mapping instances to some other type with a subset of the properties mapping lists to sets this kind of things

Joffrey · Answer

But I m not aware of any mechanism at least in the language to change the behaviour of `equals ` I m not sure what you re looking for exactly

CLOVIS · Answer

It s part of the definition of what a `List` is that order is important As long as it s a list everything in the language will take the order of account `Set` however does not declare that the order is important Some implementations ignore the order `HashSet` some take it into account `SortedSet`

David Kubecka · Answer

gt If some properties use some randomness A classic example would be DB generated ids The method under test creates some data and saves it to DB I m then checking the content of the entities Of course I can either split the code to generating and saving parts and test only the generating part set up specific DTO just for the test use case But both of them seem to be too much work for a simple task of ignoring a few properties

CLOVIS · Answer

It s not that much work ```assertEquals expected actual mapValues v gt v toSet ```

David Kubecka · Answer

< CLOVIS> I m now talking about the other part gt ignoring property values in an instance Sorry

CLOVIS · Answer

Ah yes ignoring values requires creating your own data structures

Joffrey · Answer

point up the code Ivan wrote is what I meant by you can convert both sides of the assertEquals to some other representation that matches what you want to take into account It s the same for list gt set as it is for replacing an instance with another instance with a fixed value

Joffrey · Answer

`assertEquals expected actual copy id = fixed value `

David Kubecka · Answer

Sure you can do that but that gets quite annoying once the structure has more levels of nesting

David Kubecka · Answer

Btw I m doing exctly that ^ currently and I don t like it so that s the reason why I m asking slightly smiling face

Joffrey · Answer

In your specific example above you control the DB mock if you re testing a method that creates and inserts instances so the DB mock could generate fixed IDs

Joffrey · Answer

I m still not sure what you are looking for How do you envision the code that you would like to write for this Are you looking for a way to locally change the meaning of `equals` for a given type

Joffrey · Answer

gt Sure you can do that but that gets quite annoying once the structure has more levels of nesting True that s why I usually prefer to do it right and fix the production code instead slightly smiling face

David Kubecka · Answer

I would like to do something like ```val expected = MyClass prop1 = 1 prop2 = 2 prop3 = ignore val actual = MyClass prop1 = 1 prop2 = 2 prop3 = 3 expectThat expected equals expected ```

David Kubecka · Answer

It s basically the same as the fixed value approach but it IMO expresses the intent in a much clearer way

CLOVIS · Answer

That s not possible in standard Kotlin < CT0G9SD7Z|kotest> allows creating partial matchers but it s a Other than that you d have to build your own thing

David Kubecka · Answer

Ok thank you all

Szymon Jeziorski · Answer

Assuming you re on JVM and are open to Java libraries you may want to use AssertJ You can use recursive comparison ignoring collection order to achieve what you need regardless of how many nested levels there are without manual mappings Overall AssertJ has a very robust API which can suit many edge cases ```val first = mapOf 1 to listOf 2 3 mapOf first to listOf 1 2 3 val second = mapOf 1 to listOf mapOf first to listOf 3 1 2 3 2 assertThat first usingRecursiveComparison ignoringCollectionOrder isEqualTo second this would pass```