diff --git a/depgraph/graph.go b/depgraph/graph.go
index 1cf4c15b99..7d30de1afd 100644
--- a/depgraph/graph.go
+++ b/depgraph/graph.go
@@ -11,7 +11,7 @@ import (
 	"github.com/hashicorp/terraform/digraph"
 )
 
-// Graph is used to represent the entire dependency graph
+// Graph is used to represent a dependency graph.
 type Graph struct {
 	Name  string
 	Meta  interface{}
@@ -19,58 +19,8 @@ type Graph struct {
 	Root  *Noun
 }
 
-// Validate is used to ensure that a few properties of the graph are not violated:
-// 1) There must be a single "root", or source on which nothing depends.
-// 2) All nouns in the graph must be reachable from the root
-// 3) The graph must be cycle free, meaning there are no cicular dependencies
-func (g *Graph) Validate() error {
-	// Convert to node list
-	nodes := make([]digraph.Node, len(g.Nouns))
-	for i, n := range g.Nouns {
-		nodes[i] = n
-	}
-
-	// Create a validate erro
-	vErr := &ValidateError{}
-
-	// Search for all the sources, if we have only 1, it must be the root
-	if sources := digraph.Sources(nodes); len(sources) != 1 {
-		vErr.MissingRoot = true
-		goto CHECK_CYCLES
-	} else {
-		g.Root = sources[0].(*Noun)
-	}
-
-	// Check reachability
-	if unreached := digraph.Unreachable(g.Root, nodes); len(unreached) > 0 {
-		vErr.Unreachable = make([]*Noun, len(unreached))
-		for i, u := range unreached {
-			vErr.Unreachable[i] = u.(*Noun)
-		}
-	}
-
-CHECK_CYCLES:
-	// Check for cycles
-	if cycles := digraph.StronglyConnectedComponents(nodes, true); len(cycles) > 0 {
-		vErr.Cycles = make([][]*Noun, len(cycles))
-		for i, cycle := range cycles {
-			group := make([]*Noun, len(cycle))
-			for j, n := range cycle {
-				group[j] = n.(*Noun)
-			}
-			vErr.Cycles[i] = group
-		}
-	}
-
-	// Return the detailed error
-	if vErr.MissingRoot || vErr.Unreachable != nil || vErr.Cycles != nil {
-		return vErr
-	}
-	return nil
-}
-
 // ValidateError implements the Error interface but provides
-// additional information on a validation error
+// additional information on a validation error.
 type ValidateError struct {
 	// If set, then the graph is missing a single root, on which
 	// there are no depdendencies
@@ -89,6 +39,31 @@ func (v *ValidateError) Error() string {
 	return "The depedency graph is not valid"
 }
 
+// ConstraintError is used to return detailed violation
+// information from CheckConstraints
+type ConstraintError struct {
+	Violations []*Violation
+}
+
+func (c *ConstraintError) Error() string {
+	return fmt.Sprintf("%d constraint violations", len(c.Violations))
+}
+
+// Violation is used to pass along information about
+// a constraint violation
+type Violation struct {
+	Source     *Noun
+	Target     *Noun
+	Dependency *Dependency
+	Constraint Constraint
+	Err        error
+}
+
+func (v *Violation) Error() string {
+	return fmt.Sprintf("Constraint %v between %v and %v violated: %v",
+		v.Constraint, v.Source, v.Target, v.Err)
+}
+
 // CheckConstraints walks the graph and ensures that all
 // user imposed constraints are satisfied.
 func (g *Graph) CheckConstraints() error {
@@ -129,27 +104,52 @@ func (g *Graph) CheckConstraints() error {
 	return nil
 }
 
-// ConstraintError is used to return detailed violation
-// information from CheckConstraints
-type ConstraintError struct {
-	Violations []*Violation
-}
+// Validate is used to ensure that a few properties of the graph are not violated:
+// 1) There must be a single "root", or source on which nothing depends.
+// 2) All nouns in the graph must be reachable from the root
+// 3) The graph must be cycle free, meaning there are no cicular dependencies
+func (g *Graph) Validate() error {
+	// Convert to node list
+	nodes := make([]digraph.Node, len(g.Nouns))
+	for i, n := range g.Nouns {
+		nodes[i] = n
+	}
 
-func (c *ConstraintError) Error() string {
-	return fmt.Sprintf("%d constraint violations", len(c.Violations))
-}
+	// Create a validate erro
+	vErr := &ValidateError{}
 
-// Violation is used to pass along information about
-// a constraint violation
-type Violation struct {
-	Source     *Noun
-	Target     *Noun
-	Dependency *Dependency
-	Constraint Constraint
-	Err        error
-}
+	// Search for all the sources, if we have only 1, it must be the root
+	if sources := digraph.Sources(nodes); len(sources) != 1 {
+		vErr.MissingRoot = true
+		goto CHECK_CYCLES
+	} else {
+		g.Root = sources[0].(*Noun)
+	}
 
-func (v *Violation) Error() string {
-	return fmt.Sprintf("Constraint %v between %v and %v violated: %v",
-		v.Constraint, v.Source, v.Target, v.Err)
+	// Check reachability
+	if unreached := digraph.Unreachable(g.Root, nodes); len(unreached) > 0 {
+		vErr.Unreachable = make([]*Noun, len(unreached))
+		for i, u := range unreached {
+			vErr.Unreachable[i] = u.(*Noun)
+		}
+	}
+
+CHECK_CYCLES:
+	// Check for cycles
+	if cycles := digraph.StronglyConnectedComponents(nodes, true); len(cycles) > 0 {
+		vErr.Cycles = make([][]*Noun, len(cycles))
+		for i, cycle := range cycles {
+			group := make([]*Noun, len(cycle))
+			for j, n := range cycle {
+				group[j] = n.(*Noun)
+			}
+			vErr.Cycles[i] = group
+		}
+	}
+
+	// Return the detailed error
+	if vErr.MissingRoot || vErr.Unreachable != nil || vErr.Cycles != nil {
+		return vErr
+	}
+	return nil
 }
diff --git a/depgraph/graph_test.go b/depgraph/graph_test.go
index f0bbc88898..59d3e72810 100644
--- a/depgraph/graph_test.go
+++ b/depgraph/graph_test.go
@@ -53,9 +53,26 @@ func NounMapToList(m map[string]*Noun) []*Noun {
 	return list
 }
 
-func TestGraph_Validate_NoRoot(t *testing.T) {
+func TestGraph_Validate(t *testing.T) {
 	nodes := ParseNouns(`a -> b
-b -> a`)
+a -> c
+b -> d
+b -> e
+c -> d
+c -> e`)
+	list := NounMapToList(nodes)
+
+	g := &Graph{Name: "Test", Nouns: list}
+	if err := g.Validate(); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+}
+
+func TestGraph_Validate_Cycle(t *testing.T) {
+	nodes := ParseNouns(`a -> b
+a -> c
+b -> d
+d -> b`)
 	list := NounMapToList(nodes)
 
 	g := &Graph{Name: "Test", Nouns: list}
@@ -69,8 +86,16 @@ b -> a`)
 		t.Fatalf("expected validate error")
 	}
 
-	if !vErr.MissingRoot {
-		t.Fatalf("expected missing root")
+	if len(vErr.Cycles) != 1 {
+		t.Fatalf("expected cycles")
+	}
+
+	cycle := vErr.Cycles[0]
+	if cycle[0].Name != "d" {
+		t.Fatalf("bad: %v", cycle)
+	}
+	if cycle[1].Name != "b" {
+		t.Fatalf("bad: %v", cycle)
 	}
 }
 
@@ -95,11 +120,9 @@ c -> d`)
 	}
 }
 
-func TestGraph_Validate_Unreachable(t *testing.T) {
+func TestGraph_Validate_NoRoot(t *testing.T) {
 	nodes := ParseNouns(`a -> b
-a -> c
-b -> d
-x -> x`)
+b -> a`)
 	list := NounMapToList(nodes)
 
 	g := &Graph{Name: "Test", Nouns: list}
@@ -113,20 +136,16 @@ x -> x`)
 		t.Fatalf("expected validate error")
 	}
 
-	if len(vErr.Unreachable) != 1 {
-		t.Fatalf("expected unreachable")
-	}
-
-	if vErr.Unreachable[0].Name != "x" {
-		t.Fatalf("bad: %v", vErr.Unreachable[0])
+	if !vErr.MissingRoot {
+		t.Fatalf("expected missing root")
 	}
 }
 
-func TestGraph_Validate_Cycle(t *testing.T) {
+func TestGraph_Validate_Unreachable(t *testing.T) {
 	nodes := ParseNouns(`a -> b
 a -> c
 b -> d
-d -> b`)
+x -> x`)
 	list := NounMapToList(nodes)
 
 	g := &Graph{Name: "Test", Nouns: list}
@@ -140,32 +159,12 @@ d -> b`)
 		t.Fatalf("expected validate error")
 	}
 
-	if len(vErr.Cycles) != 1 {
-		t.Fatalf("expected cycles")
-	}
-
-	cycle := vErr.Cycles[0]
-	if cycle[0].Name != "d" {
-		t.Fatalf("bad: %v", cycle)
-	}
-	if cycle[1].Name != "b" {
-		t.Fatalf("bad: %v", cycle)
+	if len(vErr.Unreachable) != 1 {
+		t.Fatalf("expected unreachable")
 	}
-}
 
-func TestGraph_Validate(t *testing.T) {
-	nodes := ParseNouns(`a -> b
-a -> c
-b -> d
-b -> e
-c -> d
-c -> e`)
-	list := NounMapToList(nodes)
-
-	g := &Graph{Name: "Test", Nouns: list}
-	err := g.Validate()
-	if err != nil {
-		t.Fatalf("err: %v", err)
+	if vErr.Unreachable[0].Name != "x" {
+		t.Fatalf("bad: %v", vErr.Unreachable[0])
 	}
 }