add some additional tests

src/instrument/priors/array_priors.jl

@@ -1,4 +1,4 @@
-struct ArrayPrior{D, A, R, C<:Union{NTuple{2, Symbol}, Nothing}}
+struct ArrayPrior{D, A, R, C}
     default_dist::D
     override_dist::A
     refant::R
@@ -30,9 +30,13 @@ means that every site has a normal prior with mean 0 and 0.1 std. dev. except LM
 zero and unit std. dev. Finally the refant is using the [`SEFDReference`](@ref) scheme.
 """
 function ArrayPrior(dist; refant=NoReference(), phase=false, centroid_station=nothing, kwargs...)
+    if centroid_station isa Tuple{<:Symbol, <:Symbol}
+        centroid_station = NamedTuple{centroid_station}((0.0, 0.0))
+    end
     return ArrayPrior(dist, kwargs, refant, phase, centroid_station)
 end
 
+
 function site_priors(d::ArrayPrior, array)
     return site_tuple(array, d.default_dist; d.override_dist...)
 end
@@ -183,13 +187,14 @@ function build_dist(dists::NamedTuple, smap::SiteLookup, array, refants, centroi
     # fs = smap.frequencies
     fixedinds, vals = reference_indices(array, smap, refants)
 
-
     if !(centroid_station isa Nothing)
-        centroid1 = findfirst(==(centroid_station[1]), ss)
-        centroid2 = findfirst(==(centroid_station[2]), ss)
+        centstat = keys(centroid_station)
+        vals = values(centroid_station)
+        centroid1 = findfirst(==(centstat[1]), ss)
+        centroid2 = findfirst(==(centstat[2]), ss)
         centroid === nothing && throw(ArgumentError("Centroid station not found in site list"))
         append!(fixedinds, [centroid1, centroid2])
-        vals = append!(collect(vals), fill(0.0, 2))
+        vals = append!(collect(vals), [vals[1], vals[2]])
     end
 
     variateinds = setdiff(eachindex(ts), fixedinds)

src/mrf_image.jl

@@ -31,8 +31,11 @@ function _apply_fluctuations(f, mimg::AbstractArray, δ::AbstractArray)
     return mimg.*f.(δ)
 end
 
+_checknorm(m::AbstractArray) = isapprox(sum(m), 1, atol=1e-6)
+Enzyme.EnzymeRules.inactive(::typeof(_checknorm), args...) = nothing
+
 function _apply_fluctuations(t::VLBIImagePriors.LogRatioTransform, mimg::AbstractArray, δ::AbstractArray)
-    @argcheck isapprox(sum(parent(mimg)), 1, atol=1e-6) "Mean image must have unit flux when using log-ratio transformations in apply_fluctuations"
+    @argcheck _checknorm(mimg) "Mean image must have unit flux when using log-ratio transformations in apply_fluctuations"
     r = to_simplex(t, δ)
     r .= r.*parent(mimg)
     r .= r./sum(r)

src/posterior/vlbiposterior.jl

@@ -87,6 +87,11 @@ function combine_prior(skymodel, ::Tuple{})
     return NamedDist((sky=skymodel,))
 end
 
+function combine_prior(skymodel::NamedDist{()}, intmodel::Tuple{})
+    return NamedDist()
+end
+
+
 function combine_prior(skymodel, ::NamedDist{()})
     return NamedDist((sky=skymodel,))
 end