Also I think are you using Juno. Do be aware that Juno development has currently stopped in favor of VSCode development. This is due to upstream Atom development slowing down.
Make sure PrimitivesTest.jl also looks like this:
module PrimitivesTest
using rtc, rtc.Primitives, ReTest
@testset "float_equality should return true" begin
@test float_equality(0.1, 0.1222)
end
end
runtests.jl should be as follows, note the . in front of .PrimitivesTest
include("PrimitivesTest.jl")
using rtc, rtc.Primitives, .PrimitivesTest
In the end we will need use include(::String).
Thank you by help @mkitti. Without your help I think never will get it working. 