diff --git a/test/Project.toml b/test/Project.toml
index 7f90c1c1b2..797d4c384e 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -9,7 +9,7 @@ InlineStrings = "842dd82b-1e85-43dc-bf29-5d0ee9dffc48"
 LLVM = "929cbde3-209d-540e-8aea-75f648917ca0"
 LLVM_jll = "86de99a1-58d6-5da7-8064-bd56ce2e322c"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
-Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
+MPI = "da04e1cc-30fd-572f-bb4f-1f8673147195"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 SpecialFunctions = "276daf66-3868-5448-9aa4-cd146d93841b"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
diff --git a/test/mpi.jl b/test/mpi.jl
new file mode 100644
index 0000000000..2988764472
--- /dev/null
+++ b/test/mpi.jl
@@ -0,0 +1,61 @@
+using MPI
+using Enzyme
+using Test
+
+struct Context
+    x::Vector{Float64}
+end
+
+function halo(context)
+    x = context.x
+    np = MPI.Comm_size(MPI.COMM_WORLD)
+    rank = MPI.Comm_rank(MPI.COMM_WORLD)
+    requests = Vector{MPI.Request}()
+    if rank != 0
+        buf =  @view x[1:1]
+        push!(requests, MPI.Isend(x[2:2], MPI.COMM_WORLD; dest=rank-1, tag=0))
+        push!(requests, MPI.Irecv!(buf, MPI.COMM_WORLD; source=rank-1, tag=0))
+    end
+    if rank != np-1
+        buf =  @view x[end:end]
+        push!(requests, MPI.Isend(x[end-1:end-1], MPI.COMM_WORLD; dest=rank+1, tag=0))
+        push!(requests, MPI.Irecv!(buf, MPI.COMM_WORLD; source=rank+1, tag=0))
+    end
+    for request in requests
+        MPI.Wait(request)
+    end
+    return nothing
+end
+
+MPI.Init()
+np = MPI.Comm_size(MPI.COMM_WORLD)
+rank = MPI.Comm_rank(MPI.COMM_WORLD)
+n = np*10
+n1 = Int(round(rank / np * (n+np))) - rank
+n2 = Int(round((rank + 1) / np * (n+np))) - rank
+nl = rank == 0 ? n1+1 : n1
+nr = rank == np-1 ? n2-1 : n2
+nlocal = nr-nl+1
+context = Context(zeros(nlocal))
+fill!(context.x, Float64(rank))
+halo(context)
+if rank != 0
+    @test context.x[1] == Float64(rank-1)
+end
+if rank != np-1
+    @test context.x[end] == Float64(rank+1)
+end
+
+dcontext = Context(zeros(nlocal))
+fill!(dcontext.x, Float64(rank))
+autodiff(Reverse, halo, Duplicated(context, dcontext))
+MPI.Barrier(MPI.COMM_WORLD)
+if rank != 0
+    @test dcontext.x[2] == Float64(rank + rank - 1)
+end
+if rank != np-1
+    @test dcontext.x[end-1] == Float64(rank + rank + 1)
+end
+if !isinteractive()
+    MPI.Finalize()
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index a796880650..5ed0be8d0b 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -21,6 +21,7 @@ using Aqua
 using Statistics
 using LinearAlgebra
 using InlineStrings
+using MPI
 
 using Enzyme_jll
 @info "Testing against" Enzyme_jll.libEnzyme
@@ -236,7 +237,7 @@ make3() = (1.0, 2.0, 3.0)
     test_scalar(x->rem(x, 1), 0.7)
     test_scalar(x->rem2pi(x,RoundDown), 0.7)
     test_scalar(x->fma(x,x+1,x/3), 2.3)
-    
+
     @test autodiff(Forward, sincos, Duplicated(1.0, 1.0))[1][1] ≈ cos(1.0)
 
     @test autodiff(Reverse, (x)->log(x), Active(2.0)) == ((0.5,),)
@@ -588,7 +589,7 @@ end
 
     bias = Float32[0.0;;;]
     res = Enzyme.autodiff(Reverse, f, Active, Active(x[1]), Const(bias))
-    
+
     @test bias[1][1] ≈ 0.0
     @test res[1][1] ≈ cos(x[1])
 end
@@ -931,7 +932,7 @@ end
 
 @inline function myquantile(v::AbstractVector, p::Real; alpha)
     n = length(v)
-    
+
     m = 1.0 + p * (1.0 - alpha - 1.0)
     aleph = n*p + oftype(p, m)
     j = clamp(trunc(Int, aleph), 1, n-1)
@@ -944,7 +945,7 @@ end
         a = @inbounds v[j]
         b = @inbounds v[j + 1]
     end
-    
+
     return a + γ*(b-a)
 end
 
@@ -1166,18 +1167,18 @@ end
 	@test 1.0 ≈ Enzyme.autodiff(Forward, inactive_gen, Duplicated(1E4, 1.0))[1]
 
     function whocallsmorethan30args(R)
-        temp = diag(R)     
-         R_inv = [temp[1] 0. 0. 0. 0. 0.; 
-             0. temp[2] 0. 0. 0. 0.; 
-             0. 0. temp[3] 0. 0. 0.; 
-             0. 0. 0. temp[4] 0. 0.; 
-             0. 0. 0. 0. temp[5] 0.; 
+        temp = diag(R)
+         R_inv = [temp[1] 0. 0. 0. 0. 0.;
+             0. temp[2] 0. 0. 0. 0.;
+             0. 0. temp[3] 0. 0. 0.;
+             0. 0. 0. temp[4] 0. 0.;
+             0. 0. 0. 0. temp[5] 0.;
          ]
-    
+
         return sum(R_inv)
     end
-    
-    R = zeros(6,6)    
+
+    R = zeros(6,6)
     dR = zeros(6, 6)
     autodiff(Reverse, whocallsmorethan30args, Active, Duplicated(R, dR))
 
@@ -1845,7 +1846,7 @@ end
     end
     # TODO: Add test for NoShadowException
 end
-    
+
 function indirectfltret(a)::DataType
     a[] *= 2
     return Float64
@@ -2313,7 +2314,7 @@ end
     Enzyme.API.runtimeActivity!(false)
     @test res[1] ≈ 0.2
     # broken as the return of an apply generic is {primal, primal}
-    # but since the return is abstractfloat doing the 
+    # but since the return is abstractfloat doing the
     @static if VERSION ≥ v"1.9-" && !(VERSION ≥ v"1.10-" )
         @test_broken res[2] ≈ 1.0
     else
@@ -2383,6 +2384,16 @@ end
     )
     @test ad_eta[1] ≈ 0.0
 end
+@testset "MPI" begin
+    testdir = @__DIR__
+    # Test parsing
+    include("mpi.jl")
+    mpiexec() do cmd
+        run(`$cmd -n 2 $(Base.julia_cmd()) --project=$testdir $testdir/mpi.jl`)
+    end
+    @test true
+end
+
 
 @testset "Tape Width" begin
     struct Roo
@@ -2452,10 +2463,10 @@ end
         Duplicated(inters, dinters),
     )
 
-    @test dinters[1].k ≈ 0.1 
-    @test dinters[1].t0 ≈ 1.0 
-    @test dinters[2].k ≈ 0.3 
-    @test dinters[2].t0 ≈ 2.0 
+    @test dinters[1].k ≈ 0.1
+    @test dinters[1].t0 ≈ 1.0
+    @test dinters[2].k ≈ 0.3
+    @test dinters[2].t0 ≈ 2.0
 end
 
 @testset "Statistics" begin
@@ -2524,7 +2535,7 @@ end
     y = A \ b
     @test dA ≈ (-z * transpose(y))
     @test db ≈ z
-    
+
     db = zero(b)
 
     forward, pullback = Enzyme.autodiff_thunk(ReverseSplitNoPrimal, Const{typeof(\)}, Duplicated, Const{typeof(A)}, Duplicated{typeof(b)})
@@ -2540,7 +2551,7 @@ end
 
     y = A \ b
     @test db ≈ z
-    
+
     dA = zero(A)
 
     forward, pullback = Enzyme.autodiff_thunk(ReverseSplitNoPrimal, Const{typeof(\)}, Duplicated, Duplicated{typeof(A)}, Const{typeof(b)})