test: separate out DiffEqIndexing into SII testset

Author: AayushSabharwal

test/runtests.jl

@@ -35,13 +35,19 @@ end
 
     if GROUP == "Downstream"
         activate_downstream_env()
-        @time @safetestset "DiffEqArray Indexing Tests" include("downstream/symbol_indexing.jl")
         @time @safetestset "ODE Solve Tests" include("downstream/odesolve.jl")
         @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")
     end
 
+    if GROUP == "SymbolicIndexingInterface" || GROUP == "Downstream"
+        if GROUP == "SymbolicIndexingInterface"
+            activate_downstream_env()
+            @time @safetestset "DiffEqArray Indexing Tests" include("downstream/symbol_indexing.jl")
+        end
+    end
+
     if GROUP == "GPU"
         activate_gpu_env()
         @time @safetestset "VectorOfArray GPU" include("gpu/vectorofarray_gpu.jl")