add ErrIntentional

Author: smoothprogrammer

testr.go

@@ -7,6 +7,9 @@ import (
 	"reflect"
 )
 
+// ErrIntentional is a sentinel error represents intentional error in the test.
+var ErrIntentional = errors.New("testr: intentional error")
+
 // T represents testing.T.
 type T interface {
 	Helper()

testr_test.go

@@ -1,7 +1,6 @@
 package testr_test
 
 import (
-	"errors"
 	"testing"
 
 	"github.com/smoothprogrammer/testr"
@@ -354,11 +353,11 @@ func TestNilT(t *testing.T) {
 func TestMust(t *testing.T) {
 	assert := testr.New(t)
 	testr.Must(nil)
-	assert.Panic(func() { testr.Must(errors.New("intentional error")) })
+	assert.Panic(func() { testr.Must(testr.ErrIntentional) })
 }
 
 func TestMustV(t *testing.T) {
 	assert := testr.New(t)
 	assert.Equal(testr.MustV("ok", nil), "ok")
-	assert.Panic(func() { testr.MustV("panic", errors.New("intentional error")) })
+	assert.Panic(func() { testr.MustV("panic", testr.ErrIntentional) })
 }