Template object type safety in createSpyObject

[szabyg]

Description

createSpyObject allows creating mock objects for services providing a template object with mock implementations of the methods of your choice. The only problem is that the type definition of the template parameter is Partial<Record<keyof T, any>> allowing to define anything as values.

export function createSpyObject<T>(type: Type<T>, template?: Partial<Record<keyof T, any>>): SpyObject<T>

See /ngneat/spectator/projects/spectator/jest/src/lib/mock.ts#L13

Would the definition be Partial<T>, the compiler would also check the value types and help to keep the unit test implementation in sync with the code to be tested.

Changing this would cause now many failing tests that were "happy" so far but probably "wrong" in the sense of type safety, and - at least in some cases also - from the logic.

This change would be very helpful when refactoring code.

Proposed solution

I propose changing the type definition to

export function createSpyObject<T>(type: Type<T>, template?: Partial<T>): SpyObject<T>

I am not sure though how to deal with backward compatibility when making type safety kick in stronger than before.

Alternatives considered

Not sure. An opt-in solution would be good to allow - especially big projects - to fix their code bit by bit.

Do you want to create a pull request?

No

[szabyg]

I could create a PR but I feel this needs a discussion first.

[NetanelBasal]

We can release a new major version.