convert Check method to return the mutation count

mutator/branch/mutateelse.go

@@ -35,11 +35,14 @@ func (m *MutatorElse) check(node ast.Node) (*ast.IfStmt, bool) {
 	return n, true
 }
 
-// Check validates if a given node can be mutated by the mutator
-func (m *MutatorElse) Check(node ast.Node) bool {
+// Check validates how often a node can be mutated by a mutator
+func (m *MutatorElse) Check(node ast.Node) uint {
 	_, ok := m.check(node)
+	if !ok {
+		return 0
+	}
 
-	return ok
+	return 1
 }
 
 // Mutate mutates a given node if it can be mutated by the mutator.

mutator/branch/mutateif.go

@@ -26,11 +26,14 @@ func (m *MutatorIf) check(node ast.Node) (*ast.IfStmt, bool) {
 	return n, ok
 }
 
-// Check validates if a given node can be mutated by the mutator
-func (m *MutatorIf) Check(node ast.Node) bool {
+// Check validates how often a node can be mutated by a mutator
+func (m *MutatorIf) Check(node ast.Node) uint {
 	_, ok := m.check(node)
+	if !ok {
+		return 0
+	}
 
-	return ok
+	return 1
 }
 
 // Mutate mutates a given node if it can be mutated by the mutator.

mutator/mutator.go

@@ -8,8 +8,8 @@ import (
 
 // Mutator defines a mutator for mutation testing
 type Mutator interface {
-	// Check validates if a given node can be mutated by the mutator
-	Check(node ast.Node) bool
+	// Check validates how often a node can be mutated by a mutator
+	Check(node ast.Node) uint
 	// Mutate mutates a given node if it can be mutated by the mutator.
 	// It first checks if the given node can be mutated by the mutator. If the node cannot be mutated, false is send into the given control channel and the method returns. If the node can be mutated, the current state of the node is saved. Afterwards the node is mutated, true is send into the given control channel and the method waits on the channel to continue the process. After receiving a value from the channel the original state of the node is restored, true is send into the given control channel and the method waits on the channel to continue the process. After receiving a value from the channel the method returns which finishes the mutation process.
 	Mutate(node ast.Node, changed chan bool)

walk.go

@@ -3,12 +3,13 @@ package mutesting
 import (
 	"fmt"
 	"go/ast"
+	"strings"
 
 	"github.com/zimmski/go-mutesting/mutator"
 )
 
-// CountWalk returns the number of corresponding nodes for a given mutator.
-// It traverses the AST of the given node and calls the method Check of the given mutator for every node. If Check returns true an internal counter is increment. After completion of the traversal the final counter is returned.
+// CountWalk returns the number of corresponding mutations for a given mutator.
+// It traverses the AST of the given node and calls the method Check of the given mutator for every node and sums up the returned counts. After completion of the traversal the final counter is returned.
 func CountWalk(node ast.Node, m mutator.Mutator) uint {
 	w := &countWalk{
 		count:   0,
@@ -27,8 +28,12 @@ type countWalk struct {
 
 // Visit implements the Visit method of the ast.Visitor interface
 func (w *countWalk) Visit(node ast.Node) ast.Visitor {
-	if w.mutator.Check(node) {
-		w.count++
+	if node == nil {
+		return w
+	}
+
+	if n := w.mutator.Check(node); n > 0 {
+		w.count += n
 	}
 
 	return w
@@ -58,7 +63,11 @@ type mutateWalk struct {
 
 // Visit implements the Visit method of the ast.Visitor interface
 func (w *mutateWalk) Visit(node ast.Node) ast.Visitor {
-	if w.mutator.Check(node) {
+	if node == nil {
+		return w
+	}
+
+	if w.mutator.Check(node) > 0 {
 		w.mutator.Mutate(node, w.changed)
 	}