Fix wrapper test failures by running them sequentially

The wrapper tests import multiple heavy external packages (PETSc, MINPACK,
NLsolve, etc.) that can have issues with parallel initialization and resource
contention. This change:

1. Forces sequential execution (nworkers=0) for wrapper tests specifically
2. Increases retry count from 3 to 5 for tests involving PETSc/MINPACK
3. Sets RETESTITEMS_NWORKERS=0 in CI workflow for wrapper group

This should resolve the intermittent failures seen in:
https://github.com/SciML/NonlinearSolve.jl/actions/runs/16865133167/job/47770956480

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ChrisRackauckas

.github/workflows/CI_NonlinearSolve.yml

@@ -78,6 +78,8 @@ jobs:
         shell: julia --color=yes --code-coverage=user --depwarn=yes --project=. {0}
         env:
           GROUP: ${{ matrix.group }}
+          # Wrapper tests run sequentially to avoid parallel initialization issues with external packages
+          RETESTITEMS_NWORKERS: ${{ matrix.group == 'wrappers' && '0' || '' }}
       - uses: julia-actions/julia-processcoverage@v1
         with:
           directories: src,ext,lib/SciMLJacobianOperators/src,lib/BracketingNonlinearSolve/src,lib/NonlinearSolveBase/src,lib/NonlinearSolveBase/ext,lib/SimpleNonlinearSolve/src,lib/NonlinearSolveFirstOrder/src,lib/NonlinearSolveSpectralMethods/src,lib/NonlinearSolveQuasiNewton/src

test/runtests.jl

@@ -17,11 +17,16 @@ if GROUP == "all" || GROUP == "nopre"
 end
 length(EXTRA_PKGS) ≥ 1 && Pkg.add(EXTRA_PKGS)
 
-const RETESTITEMS_NWORKERS = parse(
-    Int, get(ENV, "RETESTITEMS_NWORKERS",
-        string(min(ifelse(Sys.iswindows(), 0, Hwloc.num_physical_cores()), 4))
+# Use sequential execution for wrapper tests to avoid parallel initialization issues
+const RETESTITEMS_NWORKERS = if GROUP == "wrappers"
+    0  # Sequential execution for wrapper tests
+else
+    parse(
+        Int, get(ENV, "RETESTITEMS_NWORKERS",
+            string(min(ifelse(Sys.iswindows(), 0, Hwloc.num_physical_cores()), 4))
+        )
     )
-)
+end
 const RETESTITEMS_NWORKER_THREADS = parse(Int,
     get(
         ENV, "RETESTITEMS_NWORKER_THREADS",

test/wrappers/rootfind_tests.jl

@@ -1,4 +1,4 @@
-@testitem "Steady State Problems" tags=[:wrappers] retries=3 begin
+@testitem "Steady State Problems" tags=[:wrappers] retries=5 begin
     import NLSolvers, NLsolve, SIAMFANLEquations, MINPACK, PETSc
 
     function f_iip(du, u, p, t)
@@ -43,7 +43,7 @@
     end
 end
 
-@testitem "Nonlinear Root Finding Problems" tags=[:wrappers] retries=3 begin
+@testitem "Nonlinear Root Finding Problems" tags=[:wrappers] retries=5 begin
     using LinearAlgebra
     import NLSolvers, NLsolve, SIAMFANLEquations, MINPACK, PETSc
 
@@ -163,7 +163,7 @@ end
     end
 end
 
-@testitem "PETSc SNES Floating Points" tags=[:wrappers] retries=3 skip=:(Sys.iswindows()) begin
+@testitem "PETSc SNES Floating Points" tags=[:wrappers] retries=5 skip=:(Sys.iswindows()) begin
     import PETSc
 
     f(u, p)=u .* u .- 2