Add validity checks to tests

test/node_reduction.jl

@@ -51,6 +51,8 @@ import MetagraphOptimization.make_node
     insert_edge!(graph, BD, B1C_2, false)
     insert_edge!(graph, CD, C1C, false)
 
+    @test is_valid(graph)
+
     @test is_exit_node(d_exit)
     @test is_entry_node(AD)
     @test is_entry_node(BD)
@@ -74,6 +76,8 @@ import MetagraphOptimization.make_node
     @test Set(nr.input) == Set([B1D_1, B1D_2])
     push_operation!(graph, nr)
     opt = get_operations(graph)
+    
+    @test is_valid(graph)
 
     @test length(opt) == (nodeFusions = 4, nodeReductions = 0, nodeSplits = 1)
     #println("After 2 Node Reductions:\n", opt)
@@ -89,5 +93,7 @@ import MetagraphOptimization.make_node
     opt = get_operations(graph)
     @test length(opt) == (nodeFusions = 6, nodeReductions = 1, nodeSplits = 1)
     #println("After reverting to the initial state:\n", opt)
+
+    @test is_valid(graph)
 end
 println("Node Reduction Unit Tests Complete!")