Fix again the tests...

Author: amontoison

test/zygote.jl

@@ -48,8 +48,8 @@ end
 test_autodiff_backend_error()
 
 # Additional backends used for tests
-ADNLPModels.predefined_backend = Dict(
-  :zygote_backend => Dict(
+push!(ADNLPModels.predefined_backend,
+  Dict(:zygote_backend => Dict(
     :gradient_backend => ADNLPModels.ZygoteADGradient,
     :jprod_backend => ADNLPModels.ZygoteADJprod,
     :jtprod_backend => ADNLPModels.ZygoteADJtprod,