Mutator to empty cases of switches

Author: zimmski

cmd/go-mutesting/main_test.go

@@ -44,5 +44,5 @@ func TestMain(t *testing.T) {
 	out := <-bufChannel
 
 	assert.Equal(t, returnOk, exitCode)
-	assert.Contains(t, out, "The mutation score is 0.750000 (6 passed, 2 failed, 0 skipped, total is 8)")
+	assert.Contains(t, out, "The mutation score is 0.636364 (7 passed, 4 failed, 0 skipped, total is 11)")
 }

example/example.go

@@ -26,6 +26,15 @@ func foo() int {
 	bar()
 	bar()
 
+	switch {
+	case n < 20:
+		n++
+	case n > 20:
+		n--
+	default:
+		n = 0
+	}
+
 	return n
 }
 

example/example_test.go

@@ -7,5 +7,5 @@ import (
 )
 
 func TestFoo(t *testing.T) {
-	Equal(t, foo(), 15)
+	Equal(t, foo(), 16)
 }

mutator/branch/mutatecase.go

@@ -0,0 +1,64 @@
+package branch
+
+import (
+	"go/ast"
+
+	"github.com/zimmski/go-mutesting/mutator"
+)
+
+// MutatorCase implements a mutator for case
+type MutatorCase struct{}
+
+// NewMutatorCase returns a new instance of a MutatorCase mutator
+func NewMutatorCase() *MutatorCase {
+	return &MutatorCase{}
+}
+
+func init() {
+	mutator.Register(MutatorCase{}.String(), func() mutator.Mutator {
+		return NewMutatorCase()
+	})
+}
+
+func (m *MutatorCase) check(node ast.Node) (*ast.CaseClause, bool) {
+	n, ok := node.(*ast.CaseClause)
+
+	return n, ok
+}
+
+// Check validates how often a node can be mutated by a mutator
+func (m *MutatorCase) Check(node ast.Node) uint {
+	_, ok := m.check(node)
+	if !ok {
+		return 0
+	}
+
+	return 1
+}
+
+// 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.
+func (m *MutatorCase) Mutate(node ast.Node, changed chan bool) {
+	n, ok := m.check(node)
+	if !ok {
+		changed <- false
+
+		return
+	}
+
+	old := n.Body
+	n.Body = make([]ast.Stmt, 0)
+
+	changed <- true
+	<-changed
+
+	n.Body = old
+
+	changed <- true
+	<-changed
+}
+
+// String implements the String method of the Stringer interface
+func (m MutatorCase) String() string {
+	return "branch/case"
+}

mutator/branch/mutatecase_test.go

@@ -0,0 +1,16 @@
+package branch
+
+import (
+	"testing"
+
+	"github.com/zimmski/go-mutesting/test"
+)
+
+func TestMutatorCase(t *testing.T) {
+	test.Mutator(
+		t,
+		NewMutatorCase(),
+		"../../testdata/branch/mutatecase.go",
+		3,
+	)
+}

testdata/branch/mutatecase.go

@@ -0,0 +1,24 @@
+// +build example-main
+
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	i := 1
+
+	for i != 4 {
+		switch {
+		case i == 1:
+			fmt.Println(i)
+		case i == 2:
+			fmt.Println(i * 2)
+		default:
+			fmt.Println(i * 3)
+		}
+
+		i++
+	}
+}

testdata/branch/mutatecase.go.0.go

@@ -0,0 +1,24 @@
+// +build example-main
+
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	i := 1
+
+	for i != 4 {
+		switch {
+		case i == 1:
+
+		case i == 2:
+			fmt.Println(i * 2)
+		default:
+			fmt.Println(i * 3)
+		}
+
+		i++
+	}
+}

testdata/branch/mutatecase.go.1.go

@@ -0,0 +1,24 @@
+// +build example-main
+
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	i := 1
+
+	for i != 4 {
+		switch {
+		case i == 1:
+			fmt.Println(i)
+		case i == 2:
+
+		default:
+			fmt.Println(i * 3)
+		}
+
+		i++
+	}
+}

testdata/branch/mutatecase.go.2.go

@@ -0,0 +1,24 @@
+// +build example-main
+
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	i := 1
+
+	for i != 4 {
+		switch {
+		case i == 1:
+			fmt.Println(i)
+		case i == 2:
+			fmt.Println(i * 2)
+		default:
+
+		}
+
+		i++
+	}
+}