diff --git a/src/compgraph_struct.jl b/src/compgraph_struct.jl
index 1d3849e..467f9b4 100644
--- a/src/compgraph_struct.jl
+++ b/src/compgraph_struct.jl
@@ -319,7 +319,7 @@ function set_coeffs!(graph, x, cref = get_all_cref(graph))
     end
     if !(length(x) == length(cref))
         error(
-            "Vector of coefficients and defined set of coefficients" *
+            "Vector of coefficients and defined set of coefficients " *
             "do not have the same length.",
         )
     end
diff --git a/test/graph_ops.jl b/test/graph_ops.jl
index 1548ea0..dc0933f 100644
--- a/test/graph_ops.jl
+++ b/test/graph_ops.jl
@@ -67,6 +67,12 @@ using LinearAlgebra, Polynomials
     add_lincomb!(graph, :AI, 2.0, :A, 2.0, :I)
     add_mult!(graph, :Pout, :AI, :A)
     add_output!(graph, :Pout)
+    try
+        rename_node!(graph, :Z, :Z_new)
+    catch e
+        @test e isa Exception
+        @test sprint(showerror, e) == "Node Z not present in the graph."
+    end
 
     graph1 = deepcopy(graph)
     rename_node!(graph1, :AI, :B)
@@ -92,4 +98,19 @@ using LinearAlgebra, Polynomials
     del_output!(graph, :Pout)
     @test isempty(graph.outputs)
 
+    # Setting and getting coefficients
+    graph = Compgraph()
+    add_lincomb!(graph, :B, [1.0], [:A])
+    add_output!(graph, :B)
+    set_coeffs!(graph, 2.0)
+    @test graph.coeffs[:B][1] == 2.0
+    try
+        set_coeffs!(graph, [1.0, 2.0])
+    catch e
+        @test e isa Exception
+        @test sprint(showerror, e) == "Vector of coefficients and defined " *
+            "set of coefficients do not have the same length."
+    end
+    @test get_coeffs(graph) == [2.0]
+
 end
diff --git a/test/topo_order.jl b/test/topo_order.jl
index 8ea5b0d..f447c55 100644
--- a/test/topo_order.jl
+++ b/test/topo_order.jl
@@ -29,4 +29,13 @@ using LinearAlgebra
     helper[:Z2] = -1
     order = get_topo_order(g, priohelp = helper, will_not_dealloc = [:I])[1]
     @test order[1:4] == [:X1; :X2; :X3; :Z1]
+
+    add_mult!(g, :Z, :B, :B)
+    try
+        get_topo_order(g)
+    catch e
+        @test e isa Exception
+        @test sprint(showerror, e) ==
+            "Graph is disconnected. Nodes [:Z] cannot be computed."
+    end
 end