hasHeader function
Matches a response that has the specified header.
If valueMatcher is provided, also checks the header value.
Example:
expect(res, hasHeader('content-type'));
expect(res, hasHeader('content-type', 'application/json'));
expect(res, hasHeader('content-type', contains('json')));
Implementation
Matcher hasHeader(String name, [Object? valueMatcher]) =>
_HeaderMatcher(name, valueMatcher);