Add test for case insensitive duplicates

Author: MGatner

tests/system/HTTP/MessageTest.php

@@ -181,17 +181,25 @@ public function testAppendBody()
 
 	public function testSetHeaderReplacingHeader()
 	{
-			$this->message->setHeader('Accept', 'json');
+		$this->message->setHeader('Accept', 'json');
 
-				$this->assertEquals('json', $this->message->getHeaderLine('Accept'));
+		$this->assertEquals('json', $this->message->getHeaderLine('Accept'));
 	}
 
 	public function testSetHeaderDuplicateSettings()
 	{
 		$this->message->setHeader('Accept', 'json');
 		$this->message->setHeader('Accept', 'xml');
 
-			$this->assertEquals('xml', $this->message->getHeaderLine('Accept'));
+		$this->assertEquals('xml', $this->message->getHeaderLine('Accept'));
+	}
+
+	public function testSetHeaderDuplicateSettingsInsensitive()
+	{
+		$this->message->setHeader('Accept', 'json');
+		$this->message->setHeader('accept', 'xml');
+
+		$this->assertEquals('xml', $this->message->getHeaderLine('Accept'));
 	}
 
 	public function testSetHeaderArrayValues()