implement Is method to errorsx

Refactor views test using errors.Is

introduce xerrors.Is instead of errors.Is

Revert "Refactor views test using errors.Is"

This reverts commit f09d336.

internal/errorsx/errorsx.go

@@ -6,3 +6,12 @@ type String string
 func (t String) Error() string {
 	return string(t)
 }
+
+// Is reports whether String matches with the target error
+func (t String) Is(target error) bool {
+	if target == nil {
+		return false
+	}
+
+	return t.Error() == target.Error()
+}

internal/errorsx/errrorsx_test.go

@@ -0,0 +1,18 @@
+package errorsx
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestIs(t *testing.T) {
+	test := func(receiver String, target error, expected bool) {
+		if result := receiver.Is(target); result != expected {
+			t.Errorf(`expected "%s Is %s" should be %t , got: %t`, receiver, target, expected, result)
+		}
+	}
+
+	test(String("test error"), errors.New("test error"), true)
+	test(String("test error"), errors.New("different error"), false)
+	test(String("test error"), nil, false)
+}