Question: Define common `Diff`s in a shared trait

[matankdr]

I would like to define common Diff instances to be used in multiple test suites.
However, when defined something like:

trait MyCommonDiffs {
  implicit val diffA: Diff[A] = ???
  implicit val diffB: Diff[B] = ???
}

and mixed in test suite:

class MyTest extends SpecificationWithJUnit with MyCommonDiffs {
...
}

The implicit Diff instances were not recognized by matchTo matcher.
Is there any best practices of how to summon implicit Diffs defined in a common trait/lib?

cc @galtoren