public void testSetField() throws Exception {
Header header = new HeaderImpl();
header.addField(DefaultFieldParser.parse("From: mime4j@james.apache.org"));
header.addField(DefaultFieldParser.parse("Received: from foo by bar for james"));
header.addField(DefaultFieldParser.parse("Content-type: text/plain; charset=US-ASCII"));
header.addField(DefaultFieldParser.parse("ReCeIvEd: from bar by foo for james"));
header.setField(DefaultFieldParser.parse("received: from nobody by noone for james"));
assertEquals(3, header.getFields().size());
assertEquals(1, header.getFields("received").size());