@Test
 public void shouldReturnSameIfOk() {
   assertThat(cleaner.clean("*****@*****.**")).isEqualTo("*****@*****.**");
 }
 @Test
 public void shouldHandleNorwegianCharacters() {
   assertThat(cleaner.clean("blåbærsyltetøy")).isEqualTo("blåbærsyltetøy");
 }
 @Test
 public void shouldHandleEmptyText() {
   assertThat(cleaner.clean("")).isEqualTo("");
 }
 @Test
 public void shouldHandleNull() {
   assertThat(cleaner.clean(null)).isNull();
 }
 @Test
 public void shouldWashUnintendedInput() {
   assertThat(cleaner.clean("Me<script>alert('abc');</script>")).isEqualTo("Me");
 }