Move SciMLBase to downstream test env, move adjoints test

SciMLBase can't resolve against RAT v4 until the companion SciMLBase PR
(SciML/SciMLBase.jl#1297) is merged. Move it out of the main test deps
into the downstream test Project.toml.

- Remove SciMLBase from [extras] and [targets] in Project.toml
- Add SciMLBase and ForwardDiff to test/downstream/Project.toml
- Move adjoints.jl to test/downstream/ (uses ODEProblem from SciMLBase)
- Core tests now pass without SciMLBase dependency

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ChrisRackauckas

Project.toml

@@ -85,7 +85,6 @@ NLsolve = "2774e3e8-f4cf-5e23-947b-6d7e65073b56"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 SafeTestsets = "1bc83da4-3b8d-516f-aca4-4fe02f6d838f"
-SciMLBase = "0bca4576-84f4-4d90-8ffe-ffa030f20462"
 SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
@@ -96,4 +95,4 @@ Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["Aqua", "FastBroadcast", "ForwardDiff", "KernelAbstractions", "Measurements", "NLsolve", "Pkg", "Random", "SafeTestsets", "SciMLBase", "SparseArrays", "StaticArrays", "Statistics", "StructArrays", "Tables", "Test", "Unitful", "Zygote"]
+test = ["Aqua", "FastBroadcast", "ForwardDiff", "KernelAbstractions", "Measurements", "NLsolve", "Pkg", "Random", "SafeTestsets", "SparseArrays", "StaticArrays", "Statistics", "StructArrays", "Tables", "Test", "Unitful", "Zygote"]

test/downstream/Project.toml

@@ -1,10 +1,12 @@
 [deps]
 ArrayInterface = "4fba245c-0d91-5ea0-9b3e-6abc04ee57a9"
+ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 ModelingToolkit = "961ee093-0014-501f-94e3-6117800e7a78"
 MonteCarloMeasurements = "0987c9cc-fe09-11e8-30f0-b96dd679fdca"
 NLsolve = "2774e3e8-f4cf-5e23-947b-6d7e65073b56"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
 RecursiveArrayTools = "731186ca-8d62-57ce-b412-fbd966d074cd"
+SciMLBase = "0bca4576-84f4-4d90-8ffe-ffa030f20462"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 SymbolicIndexingInterface = "2efcf032-c050-4f8e-a9bb-153293bab1f5"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
@@ -14,6 +16,7 @@ Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [compat]
 ArrayInterface = "7"
+ForwardDiff = "0.10, 1"
 ModelingToolkit = "8.33, 9"
 MonteCarloMeasurements = "1.1"
 NLsolve = "4"

test/downstream/adjoints.jl

@@ -0,0 +1,100 @@
+using RecursiveArrayTools, Zygote, ForwardDiff, Test
+using SciMLBase
+
+function loss(x)
+    return sum(abs2, Array(VectorOfArray([x .* i for i in 1:5])))
+end
+
+function loss2(x)
+    return sum(abs2, Array(DiffEqArray([x .* i for i in 1:5], 1:5)))
+end
+
+function loss3(x)
+    y = VectorOfArray([x .* i for i in 1:5])
+    tmp = 0.0
+    for i in 1:5, j in 1:5
+
+        tmp += y[i, j]
+    end
+    return tmp
+end
+
+function loss4(x)
+    y = DiffEqArray([x .* i for i in 1:5], 1:5)
+    tmp = 0.0
+    for i in 1:5, j in 1:5
+
+        tmp += y[i, j]
+    end
+    return tmp
+end
+
+function loss5(x)
+    return sum(abs2, Array(ArrayPartition([x .* i for i in 1:5]...)))
+end
+
+function loss6(x)
+    _x = ArrayPartition([x .* i for i in 1:5]...)
+    _prob = ODEProblem((u, p, t) -> u, _x, (0, 1))
+    return sum(abs2, Array(_prob.u0))
+end
+
+function loss7(x)
+    _x = VectorOfArray([x .* i for i in 1:5])
+    return sum(abs2, _x .- 1)
+end
+
+# use a bunch of broadcasts to test all the adjoints
+function loss8(x)
+    _x = VectorOfArray([x .* i for i in 1:5])
+    res = copy(_x)
+    res = res .+ _x
+    res = res .+ 1
+    res = res .* _x
+    res = res .* 2.0
+    res = res .* res
+    res = res ./ 2.0
+    res = res ./ _x
+    res = 3.0 .- res
+    res = .-res
+    res = identity.(Base.literal_pow.(^, res, Val(2)))
+    res = tanh.(res)
+    res = res .+ im .* res
+    res = conj.(res) .+ real.(res) .+ imag.(res) .+ abs2.(res)
+    return sum(abs2, res)
+end
+
+function loss9(x)
+    return VectorOfArray([collect((3i):(3i + 3)) .* x for i in 1:5])
+end
+
+function loss10(x)
+    voa = VectorOfArray([i * x for i in 1:5])
+    return sum(view(voa, 2:4, 3:5))
+end
+
+function loss11(x)
+    voa = VectorOfArray([i * x for i in 1:5])
+    return sum(view(voa, :, :))
+end
+
+x = float.(6:10)
+loss(x)
+@test Zygote.gradient(loss, x)[1] == ForwardDiff.gradient(loss, x)
+@test Zygote.gradient(loss2, x)[1] == ForwardDiff.gradient(loss2, x)
+@test Zygote.gradient(loss3, x)[1] == ForwardDiff.gradient(loss3, x)
+@test Zygote.gradient(loss4, x)[1] == ForwardDiff.gradient(loss4, x)
+@test Zygote.gradient(loss5, x)[1] == ForwardDiff.gradient(loss5, x)
+@test Zygote.gradient(loss6, x)[1] == ForwardDiff.gradient(loss6, x)
+@test Zygote.gradient(loss7, x)[1] == ForwardDiff.gradient(loss7, x)
+@test Zygote.gradient(loss8, x)[1] == ForwardDiff.gradient(loss8, x)
+@test ForwardDiff.derivative(loss9, 0.0) ==
+    VectorOfArray([collect((3i):(3i + 3)) for i in 1:5])
+@test Zygote.gradient(loss10, x)[1] == ForwardDiff.gradient(loss10, x)
+@test Zygote.gradient(loss11, x)[1] == ForwardDiff.gradient(loss11, x)
+
+voa = RecursiveArrayTools.VectorOfArray(fill(rand(3), 3))
+voa_gs, = Zygote.gradient(voa) do x
+    sum(sum.(x.u))
+end
+@test voa_gs isa RecursiveArrayTools.VectorOfArray

test/runtests.jl

@@ -37,7 +37,6 @@ end
         @time @safetestset "Table traits" include("tabletraits.jl")
         @time @safetestset "StaticArrays Tests" include("copy_static_array_test.jl")
         @time @safetestset "Linear Algebra Tests" include("linalg.jl")
-        @time @safetestset "Adjoint Tests" include("adjoints.jl")
         @time @safetestset "Measurement Tests" include("measurements.jl")
     end
 
@@ -51,6 +50,7 @@ end
         @time @safetestset "Event Tests with ArrayPartition" include("downstream/downstream_events.jl")
         @time @safetestset "Measurements and Units" include("downstream/measurements_and_units.jl")
         @time @safetestset "TrackerExt" include("downstream/TrackerExt.jl")
+        @time @safetestset "Adjoint Tests" include("downstream/adjoints.jl")
     end
 
     if GROUP == "SymbolicIndexingInterface" || GROUP == "Downstream"