rest-assured/src/main/java/io/restassured/builder/ResponseSpecBuilder.java
public ResponseSpecBuilder expectHeader(String headerName, Matcher<String> expectedValueMatcher) {
        spec.header(headerName, expectedValueMatcher);
        return this;
    }
public ResponseSpecBuilder expectHeader(String headerName, Matcher<String> expectedValueMatcher) {
        spec.header(headerName, expectedValueMatcher);
        return this;
    }
Expect that a response header matches the supplied header name and hamcrest matcher.

@param headerName           The name of the expected header
@param expectedValueMatcher The Hamcrest matcher that must conform to the value
@return The builder