You should not be using push!(LOAD_PATH, ".") but instead have your package deved in the environment you set the REPL before doing the include.
In fact, if you are running test/runtests.jl you probably should be doing:
cd MyPackage.jl
julia
> import Pkg
> Pkg.activate(".")
> Pkg.instantiate(".") # Only necessary if you changed dependencies since last call.
> Pkg.test()
If you want to use include directly in the REPL, it may be necessary to replace @everywhere push!(LOAD_PATH, ".") by
@everywhere import Pkg
@everywhere Pkg.activate(".")
inside your test script, and this be executed from a folder that has a Manifest.toml where you deved you package.