test/methods: do the (still broken) Unitful test with floats and not integers (although both work)

Again, the input value x to fn needs to have non-sensible units for the
desired units to come out of the finite difference method.

Author: SeSodesa

test/methods.jl

@@ -91,10 +91,10 @@ struct NotAFunction end # not <: Function on purpose, cf #224
 
     # Integration test to ensure that Unitful-output functions can be tested.
     @testset "Unitful output" begin
-        fn(x) = 5u"J/s" * x
-        @show derivativeVal = central_fdm(5, 1)(fn, 1u"s/J")
+        fn(x) = 5.0u"J/s" * x
+        @show derivativeVal = central_fdm(5, 1)(fn, 1.0u"s/J")
         @test unit(derivativeVal) == u"J/s"
-        @test isapprox(derivativeVal, 5u"J/s"; rtol=1e-12, atol=1e-12u"J/s")
+        @test isapprox(derivativeVal, 5.0u"J/s"; rtol=1e-12, atol=1e-12u"J/s")
     end
 
     @testset "Adaptation improves estimate" begin