Actually fix the rare execution error this time

test/unit_tests_execution.jl

@@ -73,5 +73,98 @@ include("../examples/profiling_utilities.jl")
         end
     end
 
+    @testset "AB->AB large sum fusion" for _ in 1:20
+        graph = parse_dag(joinpath(@__DIR__, "..", "input", "AB->AB.txt"), ABCModel())
+
+        # push a fusion with the sum node
+        ops = get_operations(graph)
+        for fusion in ops.nodeFusions
+            if isa(fusion.input[3].task, ComputeTaskSum)
+                push_operation!(graph, fusion)
+                break
+            end
+        end
+
+        # push two more fusions with the fused node
+        for _ in 1:15
+            ops = get_operations(graph)
+            for fusion in ops.nodeFusions
+                if isa(fusion.input[3].task, FusedComputeTask)
+                    push_operation!(graph, fusion)
+                    break
+                end
+            end
+        end
+
+        # try execute
+        @test is_valid(graph)
+        expected_result = 0.00013916495566048735
+        @test isapprox(execute(graph, process_2_2, machine, particles_2_2), expected_result; rtol = 0.001)
+    end
+
+
+    @testset "AB->AB large sum fusion" for _ in 1:20
+        graph = parse_dag(joinpath(@__DIR__, "..", "input", "AB->AB.txt"), ABCModel())
+
+        # push a fusion with the sum node
+        ops = get_operations(graph)
+        for fusion in ops.nodeFusions
+            if isa(fusion.input[3].task, ComputeTaskSum)
+                push_operation!(graph, fusion)
+                break
+            end
+        end
+
+        # push two more fusions with the fused node
+        for _ in 1:15
+            ops = get_operations(graph)
+            for fusion in ops.nodeFusions
+                if isa(fusion.input[3].task, FusedComputeTask)
+                    push_operation!(graph, fusion)
+                    break
+                end
+            end
+        end
+
+        # try execute
+        @test is_valid(graph)
+        expected_result = 0.00013916495566048735
+        @test isapprox(execute(graph, process_2_2, machine, particles_2_2), expected_result; rtol = 0.001)
+    end
+
+    @testset "AB->AB fusion edge case" for _ in 1:20
+        graph = parse_dag(joinpath(@__DIR__, "..", "input", "AB->AB.txt"), ABCModel())
+
+        # push two fusions with ComputeTaskV
+        for _ in 1:2
+            ops = get_operations(graph)
+            for fusion in ops.nodeFusions
+                if isa(fusion.input[1].task, ComputeTaskV)
+                    push_operation!(graph, fusion)
+                    break
+                end
+            end
+        end
+
+        # push fusions until the end
+        cont = true
+        while cont
+            cont = false
+            ops = get_operations(graph)
+            for fusion in ops.nodeFusions
+                if isa(fusion.input[1].task, FusedComputeTask)
+                    push_operation!(graph, fusion)
+                    cont = true
+                    break
+                end
+            end
+        end
+
+        # try execute
+        @test is_valid(graph)
+        expected_result = 0.00013916495566048735
+        @test isapprox(execute(graph, process_2_2, machine, particles_2_2), expected_result; rtol = 0.001)
+    end
+
 end
 println("Execution Unit Tests Complete!")