test/methods: assume correct unit in Unitful test and remove useless test

Since the commit where the assumption about the function-likeness of
differentiated objects was made in step estimation, the correct unit
actually works.

The step with adaptive=0 was also useless, as a method with no
iterations does not converge, of course.

Author: SeSodesa

test/methods.jl

@@ -99,18 +99,14 @@ struct NotAFunction end # not <: Function on purpose, cf #224
         # NOTE: the input value unit is wrong here to make this run at all!
         # The unit should be u"s", but it has to be the inverse of the desired output unit.
         # TODO: Find out the faulty code path using a debugger.
-        twoPlaceDerivativeVal = central_fdm(5, 1)(fn, 1.0u"s/J")
-
-        unadaptedDerivativeVal = central_fdm(5, 1)(fn, 1.0u"s",0)
+        twoPlaceDerivativeVal = central_fdm(5, 1)(fn, 1.0u"s")
 
         adaptedDerivativeVal = central_fdm(5, 1)(fn, 1.0u"s",1)
 
         @test unit(twoPlaceDerivativeVal) == u"J/s"
-        @test unit(unadaptedDerivativeVal) == u"J/s"
         @test unit(adaptedDerivativeVal) == u"J/s"
 
         @test isapprox(twoPlaceDerivativeVal, 5.0u"J/s"; rtol=1e-12, atol=1e-12u"J/s")
-        @test isapprox(unadaptedDerivativeVal, 5.0u"J/s"; rtol=1e-12, atol=1e-12u"J/s")
         @test isapprox(adaptedDerivativeVal, 5.0u"J/s"; rtol=1e-12, atol=1e-12u"J/s")
     end