diff --git a/docs/make.jl b/docs/make.jl
index 142681d..578cdb5 100644
--- a/docs/make.jl
+++ b/docs/make.jl
@@ -16,6 +16,7 @@ makedocs(
         "index.md",
         "Manual" => "manual.md",
         "Library" => [
+            "Public" => "lib/public.md",
             "Graph" => "lib/internals/graph.md",
             "Node" => "lib/internals/node.md",
             "Task" => "lib/internals/task.md",
diff --git a/src/MetagraphOptimization.jl b/src/MetagraphOptimization.jl
index 6188bfd..1e8c0c9 100644
--- a/src/MetagraphOptimization.jl
+++ b/src/MetagraphOptimization.jl
@@ -15,6 +15,8 @@ export AbstractComputeTask
 export AbstractDataTask
 export DataTask
 export FusedComputeTask
+export PossibleOperations
+export GraphProperties
 
 export make_node
 export make_edge
diff --git a/src/properties/utility.jl b/src/properties/utility.jl
index 6f2220e..bf936db 100644
--- a/src/properties/utility.jl
+++ b/src/properties/utility.jl
@@ -52,6 +52,7 @@ function -(prop::GraphProperties)
         data = -prop.data,
         computeEffort = -prop.computeEffort,
         computeIntensity = prop.computeIntensity,   # no negation here!
+        cost = -prop.cost,
         noNodes = -prop.noNodes,
         noEdges = -prop.noEdges,
     )::GraphProperties
diff --git a/test/runtests.jl b/test/runtests.jl
index 74f7f81..2ea1a76 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -5,6 +5,7 @@ using Test
     include("unit_tests_utility.jl")
     include("unit_tests_tasks.jl")
     include("unit_tests_nodes.jl")
+    include("unit_tests_properties.jl")
     include("node_reduction.jl")
     include("unit_tests_graph.jl")
 
diff --git a/test/unit_tests_properties.jl b/test/unit_tests_properties.jl
new file mode 100644
index 0000000..97a53ad
--- /dev/null
+++ b/test/unit_tests_properties.jl
@@ -0,0 +1,52 @@
+
+@testset "GraphProperties Unit Tests" begin
+    prop = GraphProperties()
+
+    @test prop.data == 0.0
+    @test prop.computeEffort == 0.0
+    @test prop.computeIntensity == 0.0
+    @test prop.cost == 0.0
+    @test prop.noNodes == 0.0
+    @test prop.noEdges == 0.0
+
+    prop2 = (
+        data = 5.0,
+        computeEffort = 6.0,
+        computeIntensity = 6.0 / 5.0,
+        cost = 0.0,
+        noNodes = 2,
+        noEdges = 3,
+    )::GraphProperties
+
+    @test prop + prop2 == prop2
+    @test prop2 - prop == prop2
+
+    negProp = -prop2
+    @test negProp.data == -5.0
+    @test negProp.computeEffort == -6.0
+    @test negProp.computeIntensity == 6.0 / 5.0
+    @test negProp.cost == 0.0
+    @test negProp.noNodes == -2
+    @test negProp.noEdges == -3
+
+    @test negProp + prop2 == GraphProperties()
+
+    prop3 = (
+        data = 7.0,
+        computeEffort = 3.0,
+        computeIntensity = 7.0 / 3.0,
+        cost = 0.0,
+        noNodes = -3,
+        noEdges = 2,
+    )::GraphProperties
+
+    propSum = prop2 + prop3
+
+    @test propSum.data == 12.0
+    @test propSum.computeEffort == 9.0
+    @test propSum.computeIntensity == 9.0 / 12.0
+    @test propSum.cost == 0.0
+    @test propSum.noNodes == -1
+    @test propSum.noEdges == 5
+end
+println("GraphProperties Unit Tests Complete!")