How to test an object's private methods in Scala

Question

I have an example object:

object Foo {
  private def sayFoo = \"Foo!\"
}

And I want to test the private sayFoo method without the following

Answer 1

Probably someone has done this already: How about an annotation macro @Testable that emits the object with a method that exposes the private members, but only when compiling for testing (and just the object otherwise).

scala> object X { private def f = 42 ; def g = 2 * f }
defined object X

scala> X.g
res1: Int = 84

scala> object X { private def f = 42 ; def g = 2 * f ; def testable = new { def f = X.this.f } }
defined object X

scala> X.testable.f
warning: there was one feature warning; re-run with -feature for details
res2: Int = 42

scala> object X { private def f = 42 ; def g = 2 * f ; def testable = new Dynamic { def selectDynamic(name: String) = X.this.f } }
defined object X

scala> X.testable.f
warning: there was one feature warning; re-run with -feature for details
res4: Int = 42

Alternatively, it could emit a different object TestableX.