Similar to #2159, but for a Set:
HttpHeaders headers = new HttpHeaders();
headers.add("Header", "foo");
// case-insensitive
Set<String> set = headers.headerNames();
Assertions.assertThat(set.contains("header")).isTrue(); // succeeds
Assertions.assertThat(set).contains("header"); // fails
This is org.springframework.http.HttpHeaders, but applies to any case-insensitive Set.
Impacted Assertions