Less verbose Mock declarations

[alestiago]

Problem
Currently defining a Mock looks like this:

class _MockDog extends Mock implements Dog {}
final Dog mockDog = _MockDog();

Solution I would like
I would like to have a one-line syntax alternative (or completely remove the old syntax):

final Dog mockDog = Mock<Dog>();

The advantages are:

• Reduces the chances of creating a public Mock being shared, which leads to non self contained test files.
• Reduces file pollution, sometimes a test file can have multiple mocks and the class definitions of such pollutes the readability of the file.
• Somewhat forces developers that want to have any directly implemented
  overridden fields or methods in a Mock to use a Fake. As detailed by the documentation ("A class which extends Mock should not have any directly implemented overridden fields or methods" ).

Additional notes
I'm willing to work on a pull request for this change if there is an agreement on the new syntax. As far as I am concerned having something exactly like the proposed solution would lead to a breaking change (depends on Dart's current and future capabilities). I'm opened to read about solutions that will avoid introducing a breaking change with the new syntax. I believe that a breaking change can be justified since the new syntax has many advantages and solves a couple of problems (as outlined in Additional Context).

[felangel]

Hi @alestiago thanks for opening the issue!

Do you have an idea for what the implementation would look like? I don’t see how you would be able to achieve the following:

final Dog mockDog = Mock<Dog>();

because you would be creating an instance of a Mock and if that object doesn’t extend or implement Dog, it cannot be assigned to a variable of type Dog unless I’m missing something.

Do you have a simple POC to illustrate how this proposal would be implemented?

Thanks again!

[alestiago]

@felangel I don't have a POC to illustrate how the one line example syntax can be implemented (I tried though). I think it is not possible in Dart 2.19.0 without code generation and/or mirrors.

The most obvious solution would be to do as follows, but is currently not possible to do:

class Mock<T> implements T {}

The one liner final Dog mockDog = Mock<Dog>() is what I would wish to have; but anything that results in a single line that satisfies final Dog mockDog = *; (where * denotes any expression) would suffice as long as mockDog is mockable and no code generation (build runner) is required.

Regardless of it being currently possible I wanted to open the issue to describe the most ideal scenario. Maybe there exists a way to satisfy the above statement right now that I'm not aware of. Or maybe feature Dart versions allow satisfying the above.

The aim of the issue is to encourage other developers to tackle the problem and to have a written specification of the ideal API for creating mocks.

It would be a dream 🤩 to do something as:

final Dog mockDog = Mock<Dog>();

Thanks for the package 💙 and fast reply!

[tenhobi]

Exploring some options using the upcoming Dart's static generation would be interesting for sure.