fix tests

Author: Miha Zgubic

src/rulesets/Base/mapreduce.jl

@@ -89,7 +89,15 @@ function rrule(
 end
 
 # https://github.com/JuliaDiff/ChainRules.jl/issues/522
-@opt_out ChainRulesCore.rrule(config::RuleConfig{>:HasReverseMode}, ::typeof(sum), x::AbstractArray, y::AbstractArray; dims=:)
+# The rule above assumes `f` is callable. Arrays are not, this came up when summing
+# arrays with weights in StatsBase
+@opt_out ChainRulesCore.rrule(
+    config::RuleConfig{>:HasReverseMode},
+    ::typeof(sum),
+    x::AbstractArray,
+    y::AbstractArray;
+    dims=:
+)
 
 function frule(
     (_, _, Δx),

test/rulesets/Base/mapreduce.jl

@@ -91,7 +91,7 @@
     end
 
     # https://github.com/JuliaDiff/ChainRules.jl/issues/522
-    @begin "sum(xs, weights) (#522)" begin
+    @testset "sum(xs, weights) (#522)" begin
         xs = rand(5)
         weights = rand(5)
         Base.sum(xs::AbstractArray, weights::AbstractArray) = dot(xs, weights)