diff --git a/terraform/graph.go b/terraform/graph.go
index 175db7b86..22866dc82 100644
--- a/terraform/graph.go
+++ b/terraform/graph.go
@@ -73,6 +73,16 @@ func Graph(c *config.Config, s *State) *depgraph.Graph {
 	return g
 }
 
+// GraphFull completes the raw graph returned by Graph by initializing
+// all the resource providers.
+//
+// This may add new nodes to the graph, since it can add new resource
+// providers based on the mapping given in the case that a provider
+// configuration was not specified.
+//
+// Various errors can be returned from this function, such as if there
+// is no matching provider for a resource, a resource provider can't be
+// created, etc.
 func GraphFull(g *depgraph.Graph, ps map[string]ResourceProviderFactory) error {
 	// Add missing providers from the mapping
 	if err := graphAddMissingResourceProviders(g, ps); err != nil {
diff --git a/terraform/graph_test.go b/terraform/graph_test.go
index dd721dc07..76a795e2a 100644
--- a/terraform/graph_test.go
+++ b/terraform/graph_test.go
@@ -52,6 +52,63 @@ func TestGraph_state(t *testing.T) {
 	}
 }
 
+func TestGraphFull(t *testing.T) {
+	rpAws := new(MockResourceProvider)
+	rpOS := new(MockResourceProvider)
+
+	rpAws.ResourcesReturn = []ResourceType{
+		ResourceType{Name: "aws_instance"},
+		ResourceType{Name: "aws_load_balancer"},
+		ResourceType{Name: "aws_security_group"},
+	}
+	rpOS.ResourcesReturn = []ResourceType{
+		ResourceType{Name: "openstack_floating_ip"},
+	}
+
+	ps := map[string]ResourceProviderFactory{
+		"aws":  testProviderFuncFixed(rpAws),
+		"open": testProviderFuncFixed(rpOS),
+	}
+
+	c := testConfig(t, "graph-basic")
+	g := Graph(c, nil)
+	if err := GraphFull(g, ps); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if err := g.Validate(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// A helper to help get us the provider for a resource.
+	graphProvider := func(n string) ResourceProvider {
+		return g.Noun(n).Meta.(*GraphNodeResource).Resource.Provider
+	}
+
+	// Test a couple
+	if graphProvider("aws_instance.web") != rpAws {
+		t.Fatalf("bad: %#v", graphProvider("aws_instance.web"))
+	}
+	if graphProvider("openstack_floating_ip.random") != rpOS {
+		t.Fatalf("bad: %#v", graphProvider("openstack_floating_ip.random"))
+	}
+
+	// Test that all providers have been set
+	for _, n := range g.Nouns {
+		switch m := n.Meta.(type) {
+		case *GraphNodeResource:
+			if m.Resource.Provider == nil {
+				t.Fatalf("bad: %#v", m)
+			}
+		case *GraphNodeResourceProvider:
+			if len(m.Providers) == 0 {
+				t.Fatalf("bad: %#v", m)
+			}
+		default:
+			continue
+		}
+	}
+}
+
 const testTerraformGraphStr = `
 root: root
 aws_instance.web
diff --git a/terraform/terraform_test.go b/terraform/terraform_test.go
index 2d958d2b1..2f425be29 100644
--- a/terraform/terraform_test.go
+++ b/terraform/terraform_test.go
@@ -110,46 +110,6 @@ func TestTerraformApply_vars(t *testing.T) {
 	}
 }
 
-func TestTerraformGraph(t *testing.T) {
-	rpAws := new(MockResourceProvider)
-	rpOS := new(MockResourceProvider)
-
-	rpAws.ResourcesReturn = []ResourceType{
-		ResourceType{Name: "aws_instance"},
-		ResourceType{Name: "aws_load_balancer"},
-		ResourceType{Name: "aws_security_group"},
-	}
-	rpOS.ResourcesReturn = []ResourceType{
-		ResourceType{Name: "openstack_floating_ip"},
-	}
-
-	tf := testTerraform2(t, &Config{
-		Providers: map[string]ResourceProviderFactory{
-			"aws":  testProviderFuncFixed(rpAws),
-			"open": testProviderFuncFixed(rpOS),
-		},
-	})
-
-	c := testConfig(t, "graph-basic")
-
-	g, err := tf.Graph(c, nil)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	// A helper to help get us the provider for a resource.
-	graphProvider := func(n string) ResourceProvider {
-		return g.Noun(n).Meta.(*GraphNodeResource).Resource.Provider
-	}
-
-	if graphProvider("aws_instance.web") != rpAws {
-		t.Fatalf("bad: %#v", graphProvider("aws_instance.web"))
-	}
-	if graphProvider("openstack_floating_ip.random") != rpOS {
-		t.Fatalf("bad: %#v", graphProvider("openstack_floating_ip.random"))
-	}
-}
-
 func TestTerraformPlan(t *testing.T) {
 	tf := testTerraform(t, "plan-good")