fix: skip zygote on 1.12

Author: avik-pal

lib/LuxTestUtils/Project.toml

@@ -1,6 +1,6 @@
 name = "LuxTestUtils"
 uuid = "ac9de150-d08f-4546-94fb-7472b5760531"
-version = "2.1.0"
+version = "2.2.0"
 authors = ["Avik Pal <avikpal@mit.edu>"]
 
 [deps]

lib/LuxTestUtils/src/autodiff.jl

@@ -181,10 +181,11 @@ function test_gradients(
 
     # Choose the backends to test
     backends = []
-    push!(backends, AutoZygote())
+    if ZYGOTE_TESTING_ENABLED[]
+        push!(backends, AutoZygote())
+    end
     if !on_gpu
         total_length ≤ 32 && push!(backends, AutoForwardDiff())
-        # TODO: Move Enzyme out of here once it supports GPUs
         if enable_enzyme_reverse_mode || ENZYME_TESTING_ENABLED[]
             mode = if enzyme_set_runtime_activity
                 Enzyme.set_runtime_activity(Enzyme.Reverse)
@@ -210,6 +211,11 @@ function test_gradients(
         typeof(backend).name.name != typeof(ground_truth_backend).name.name
     ]
 
+    if isempty(backends)
+        @warn "No backends to test. Skipping test..."
+        return nothing
+    end
+
     return @testset "gradtest($(f))" begin
         @testset "$(nameof(typeof(backend)))()" for backend in backends
             local_test_expr = :([$(nameof(typeof(backend)))] - $(test_expr))