@Test
void mediaType() {

    assertThat(httpClient.mediaType(null)).isNull();
    assertThat(httpClient.mediaType(ContentType.APPLICATION_JSON))
            .isSameAs(httpClient.mediaType(ContentType.APPLICATION_JSON));
    assertThat(httpClient.mediaType(ContentType.APPLICATION_FORM_URLENCODED).toString())
            .isEqualTo(ContentType.APPLICATION_FORM_URLENCODED.mediaType);
}