diff --git a/examples/get_relative.php b/examples/get_relative.php
new file mode 100644
index 0000000..d21d6b6
--- /dev/null
+++ b/examples/get_relative.php
@@ -0,0 +1,20 @@
+<?php
+require __DIR__ . '/../vendor/autoload.php';
+
+use \Curl\Curl;
+
+$curl = new Curl('https://www.example.com/api/');
+
+// https://www.example.com/api/test?key=value
+$response = $curl->get('test', array(
+    'key' => 'value',
+));
+assert('https://www.example.com/api/test?key=value' === $curl->url);
+assert($curl->url === $curl->effectiveUrl);
+
+// https://www.example.com/root?key=value
+$response = $curl->get('/root', array(
+    'key' => 'value',
+));
+assert('https://www.example.com/root?key=value' === $curl->url);
+assert($curl->url === $curl->effectiveUrl);
diff --git a/src/Curl/Curl.php b/src/Curl/Curl.php
index b582a3e..0252fec 100644
--- a/src/Curl/Curl.php
+++ b/src/Curl/Curl.php
@@ -25,7 +25,6 @@ class Curl
     public $httpStatusCode = 0;
     public $httpErrorMessage = null;
 
-    public $baseUrl = null;
     public $url = null;
     public $requestHeaders = null;
     public $responseHeaders = null;
@@ -59,7 +58,7 @@ class Curl
     private $defaultDecoder = null;
 
     public static $RFC2616 = array(
-        // RFC2616: "any CHAR except CTLs or separators".
+        // RFC 2616: "any CHAR except CTLs or separators".
         // CHAR           = <any US-ASCII character (octets 0 - 127)>
         // CTL            = <any US-ASCII control character
         //                  (octets 0 - 31) and DEL (127)>
@@ -76,7 +75,7 @@ class Curl
         'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '|', '~',
     );
     public static $RFC6265 = array(
-        // RFC6265: "US-ASCII characters excluding CTLs, whitespace DQUOTE, comma, semicolon, and backslash".
+        // RFC 6265: "US-ASCII characters excluding CTLs, whitespace DQUOTE, comma, semicolon, and backslash".
         // %x21
         '!',
         // %x23-2B
@@ -261,7 +260,7 @@ class Curl
         if (is_array($url)) {
             $data = $query_parameters;
             $query_parameters = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
 
         $this->setUrl($url, $query_parameters);
@@ -390,6 +389,10 @@ class Curl
         }
         $this->errorMessage = $this->curlError ? $this->curlErrorMessage : $this->httpErrorMessage;
 
+        // Reset select deferred properties so that they may be recalculated.
+        unset($this->effectiveUrl);
+        unset($this->totalTime);
+
         // Allow multicurl to attempt retry as needed.
         if ($this->isChildOfMultiCurl) {
             return;
@@ -433,7 +436,7 @@ class Curl
     {
         if (is_array($url)) {
             $data = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
         $this->setUrl($url, $data);
         $this->setOpt(CURLOPT_CUSTOMREQUEST, 'GET');
@@ -487,7 +490,7 @@ class Curl
     {
         if (is_array($url)) {
             $data = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
         $this->setUrl($url, $data);
         $this->setOpt(CURLOPT_CUSTOMREQUEST, 'HEAD');
@@ -508,7 +511,7 @@ class Curl
     {
         if (is_array($url)) {
             $data = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
         $this->setUrl($url, $data);
         $this->removeHeader('Content-Length');
@@ -529,7 +532,7 @@ class Curl
     {
         if (is_array($url)) {
             $data = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
 
         if (is_array($data) && empty($data)) {
@@ -572,7 +575,7 @@ class Curl
         if (is_array($url)) {
             $follow_303_with_post = (bool)$data;
             $data = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
 
         $this->setUrl($url);
@@ -613,7 +616,7 @@ class Curl
     {
         if (is_array($url)) {
             $data = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
         $this->setUrl($url);
         $this->setOpt(CURLOPT_CUSTOMREQUEST, 'PUT');
@@ -642,7 +645,7 @@ class Curl
     {
         if (is_array($url)) {
             $data = $url;
-            $url = $this->baseUrl;
+            $url = (string)$this->url;
         }
         $this->setUrl($url);
         $this->setOpt(CURLOPT_CUSTOMREQUEST, 'SEARCH');
@@ -1071,8 +1074,14 @@ class Curl
      */
     public function setUrl($url, $mixed_data = '')
     {
-        $this->baseUrl = $url;
-        $this->url = $this->buildUrl($url, $mixed_data);
+        $built_url = $this->buildUrl($url, $mixed_data);
+
+        if ($this->url === null) {
+            $this->url = (string)new Url($built_url);
+        } else {
+            $this->url = (string)new Url($this->url, $built_url);
+        }
+
         $this->setOpt(CURLOPT_URL, $this->url);
     }
 
diff --git a/src/Curl/StrUtil.php b/src/Curl/StrUtil.php
new file mode 100644
index 0000000..b32cfaf
--- /dev/null
+++ b/src/Curl/StrUtil.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Curl;
+
+class StrUtil
+{
+    /**
+     * Return true when $haystack starts with $needle.
+     *
+     * @access public
+     * @param  $haystack
+     * @param  $needle
+     *
+     * @return bool
+     */
+    public static function startsWith($haystack, $needle)
+    {
+        return mb_substr($haystack, 0, mb_strlen($needle)) === $needle;
+    }
+}
diff --git a/src/Curl/Url.php b/src/Curl/Url.php
new file mode 100644
index 0000000..68f65ef
--- /dev/null
+++ b/src/Curl/Url.php
@@ -0,0 +1,175 @@
+<?php
+
+namespace Curl;
+
+use Curl\StrUtil;
+
+class Url
+{
+    private $baseUrl = null;
+    private $relativeUrl = null;
+
+    public function __construct($base_url, $relative_url = null)
+    {
+        $this->baseUrl = $base_url;
+        $this->relativeUrl = $relative_url;
+    }
+
+    public function __toString()
+    {
+        return $this->absolutizeUrl();
+    }
+
+    /**
+     * Remove dot segments.
+     *
+     * Interpret and remove the special "." and ".." path segments from a referenced path.
+     */
+    public static function removeDotSegments($input)
+    {
+        // 1.  The input buffer is initialized with the now-appended path
+        //     components and the output buffer is initialized to the empty
+        //     string.
+        $output = '';
+
+        // 2.  While the input buffer is not empty, loop as follows:
+        while (!empty($input)) {
+
+            // A.  If the input buffer begins with a prefix of "../" or "./",
+            //     then remove that prefix from the input buffer; otherwise,
+            if (StrUtil::startsWith($input, '../')) {
+                $input = substr($input, 3);
+            } elseif (StrUtil::startsWith($input, './')) {
+                $input = substr($input, 2);
+
+            // B.  if the input buffer begins with a prefix of "/./" or "/.",
+            //     where "." is a complete path segment, then replace that
+            //     prefix with "/" in the input buffer; otherwise,
+            } elseif (StrUtil::startsWith($input, '/./')) {
+                $input = substr($input, 2);
+            } elseif ($input === '/.') {
+                $input = '/';
+
+            // C.  if the input buffer begins with a prefix of "/../" or "/..",
+            //     where ".." is a complete path segment, then replace that
+            //     prefix with "/" in the input buffer and remove the last
+            //     segment and its preceding "/" (if any) from the output
+            //     buffer; otherwise,
+            } elseif (StrUtil::startsWith($input, '/../')) {
+                $input = substr($input, 3);
+                $output = substr_replace($output, '', mb_strrpos($output, '/'));
+            } elseif ($input === '/..') {
+                $input = '/';
+                $output = substr_replace($output, '', mb_strrpos($output, '/'));
+
+            // D.  if the input buffer consists only of "." or "..", then remove
+            //     that from the input buffer; otherwise,
+            } elseif ($input === '.' || $input === '..') {
+                $input = '';
+
+            // E.  move the first path segment in the input buffer to the end of
+            //     the output buffer, including the initial "/" character (if
+            //     any) and any subsequent characters up to, but not including,
+            //     the next "/" character or the end of the input buffer.
+            } elseif (!(($pos = mb_strpos($input, '/', 1)) === false)) {
+                $output .= substr($input, 0, $pos);
+                $input = substr_replace($input, '', 0, $pos);
+            } else {
+                $output .= $input;
+                $input = '';
+            }
+        }
+
+        // 3.  Finally, the output buffer is returned as the result of
+        //     remove_dot_segments.
+        return $output . $input;
+    }
+
+    /**
+     * Absolutize url.
+     *
+     * Combine the base and relative url into an absolute url.
+     */
+    private function absolutizeUrl()
+    {
+        $b = $this->parseUrl($this->baseUrl);
+
+        if (!($this->relativeUrl === null)) {
+            $r = $this->parseUrl($this->relativeUrl);
+
+            // Copy relative parts to base url.
+            if (isset($r['scheme'])) {
+                $b['scheme'] = $r['scheme'];
+            }
+            if (isset($r['host'])) {
+                $b['host'] = $r['host'];
+            }
+            if (isset($r['port'])) {
+                $b['port'] = $r['port'];
+            }
+            if (isset($r['user'])) {
+                $b['user'] = $r['user'];
+            }
+            if (isset($r['pass'])) {
+                $b['pass'] = $r['pass'];
+            }
+
+            if (!isset($r['path']) || $r['path'] === '') {
+                $r['path'] = '/';
+            }
+            // Merge relative url with base when relative url's path doesn't start with a slash.
+            if (!(StrUtil::startsWith($r['path'], '/'))) {
+                $base = mb_strrchr($b['path'], '/', true);
+                if ($base === false) {
+                    $base = '';
+                }
+                $r['path'] = $base . '/' . $r['path'];
+            }
+            $b['path'] = $r['path'];
+            $b['path'] = $this->removeDotSegments($b['path']);
+
+            if (isset($r['query'])) {
+                $b['query'] = $r['query'];
+            }
+            if (isset($r['fragment'])) {
+                $b['fragment'] = $r['fragment'];
+            }
+        }
+
+        if (!isset($b['path'])) {
+            $b['path'] = '/';
+        }
+
+        $absolutized_url = $this->unparseUrl($b);
+        return $absolutized_url;
+    }
+
+    /**
+     * Parse url.
+     *
+     * Parse url into components of a URI as specified by RFC 3986.
+     */
+    private function parseUrl($url)
+    {
+        return parse_url($url);
+    }
+
+    /**
+     * Unparse url.
+     *
+     * Combine url components into a url.
+     */
+    private function unparseUrl($parsed_url) {
+        $scheme   = isset($parsed_url['scheme'])   ? $parsed_url['scheme'] . '://' : '';
+        $host     = isset($parsed_url['host'])     ? $parsed_url['host'] : '';
+        $port     = isset($parsed_url['port'])     ? ':' . $parsed_url['port'] : '';
+        $user     = isset($parsed_url['user'])     ? $parsed_url['user'] : '';
+        $pass     = isset($parsed_url['pass'])     ? ':' . $parsed_url['pass'] : '';
+        $pass     = ($user || $pass)               ? $pass . '@' : '';
+        $path     = isset($parsed_url['path'])     ? $parsed_url['path'] : '';
+        $query    = isset($parsed_url['query'])    ? '?' . $parsed_url['query'] : '';
+        $fragment = isset($parsed_url['fragment']) ? '#' . $parsed_url['fragment'] : '';
+        $unparsed_url =  $scheme . $user . $pass . $host . $port . $path . $query . $fragment;
+        return $unparsed_url;
+    }
+}
diff --git a/tests/PHPCurlClass/PHPCurlClassTest.php b/tests/PHPCurlClass/PHPCurlClassTest.php
index 700d5ff..61b7cb4 100644
--- a/tests/PHPCurlClass/PHPCurlClassTest.php
+++ b/tests/PHPCurlClass/PHPCurlClassTest.php
@@ -2,8 +2,8 @@
 
 namespace CurlTest;
 
-use \Curl\Curl;
 use \Curl\CaseInsensitiveArray;
+use \Curl\Curl;
 use \Helper\Test;
 
 class CurlTest extends \PHPUnit\Framework\TestCase
@@ -105,43 +105,36 @@ class CurlTest extends \PHPUnit\Framework\TestCase
         // curl -v --get --request GET "http://127.0.0.1:8000/" --data "foo=bar"
         $test = new Test();
         $test->server('server', 'GET', $data);
-        $this->assertEquals(Test::TEST_URL, $test->curl->baseUrl);
         $this->assertEquals(Test::TEST_URL . '?' . http_build_query($data), $test->curl->url);
 
         // curl -v --request POST "http://127.0.0.1:8000/" --data "foo=bar"
         $test = new Test();
         $test->server('server', 'POST', $data);
-        $this->assertEquals(Test::TEST_URL, $test->curl->baseUrl);
         $this->assertEquals(Test::TEST_URL, $test->curl->url);
 
         // curl -v --request PUT "http://127.0.0.1:8000/" --data "foo=bar"
         $test = new Test();
         $test->server('server', 'PUT', $data);
-        $this->assertEquals(Test::TEST_URL, $test->curl->baseUrl);
         $this->assertEquals(Test::TEST_URL, $test->curl->url);
 
         // curl -v --request PATCH "http://127.0.0.1:8000/" --data "foo=bar"
         $test = new Test();
         $test->server('server', 'PATCH', $data);
-        $this->assertEquals(Test::TEST_URL, $test->curl->baseUrl);
         $this->assertEquals(Test::TEST_URL, $test->curl->url);
 
         // curl -v --request DELETE "http://127.0.0.1:8000/?foo=bar"
         $test = new Test();
         $test->server('server', 'DELETE', $data);
-        $this->assertEquals(Test::TEST_URL, $test->curl->baseUrl);
         $this->assertEquals(Test::TEST_URL . '?' . http_build_query($data), $test->curl->url);
 
         // curl -v --get --request HEAD --head "http://127.0.0.1:8000/" --data "foo=bar"
         $test = new Test();
         $test->server('server', 'HEAD', $data);
-        $this->assertEquals(Test::TEST_URL, $test->curl->baseUrl);
         $this->assertEquals(Test::TEST_URL . '?' . http_build_query($data), $test->curl->url);
 
         // curl -v --get --request OPTIONS "http://127.0.0.1:8000/" --data "foo=bar"
         $test = new Test();
         $test->server('server', 'OPTIONS', $data);
-        $this->assertEquals(Test::TEST_URL, $test->curl->baseUrl);
         $this->assertEquals(Test::TEST_URL . '?' . http_build_query($data), $test->curl->url);
     }
 
@@ -152,49 +145,41 @@ class CurlTest extends \PHPUnit\Framework\TestCase
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'delete_with_body');
         $curl->delete($data, array('wibble' => 'wubble'));
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('{"get":{"key":"value"},"delete":{"wibble":"wubble"}}', $curl->rawResponse);
 
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'get');
         $curl->delete($data);
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('key=value', $curl->response);
 
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'get');
         $curl->get($data);
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('key=value', $curl->response);
 
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'get');
         $curl->head($data);
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('HEAD /?key=value HTTP/1.1', $curl->requestHeaders['Request-Line']);
 
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'get');
         $curl->options($data);
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('key=value', $curl->response);
 
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'request_method');
         $curl->patch($data);
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('PATCH', $curl->response);
 
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'post');
         $curl->post($data);
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('key=value', $curl->response);
 
         $curl = new Curl(Test::TEST_URL);
         $curl->setHeader('X-DEBUG-TEST', 'put');
         $curl->put($data);
-        $this->assertEquals(Test::TEST_URL, $curl->baseUrl);
         $this->assertEquals('key=value', $curl->response);
     }
 
@@ -255,6 +240,12 @@ class CurlTest extends \PHPUnit\Framework\TestCase
         $test->curl->setOpt(CURLOPT_FOLLOWLOCATION, true);
         $test->server('redirect', 'GET');
         $this->assertEquals(Test::TEST_URL . '?redirect', $test->curl->effectiveUrl);
+
+        $test = new Test();
+        $test->server('get', 'GET');
+        $this->assertEquals(Test::TEST_URL, $test->curl->effectiveUrl);
+        $test->server('get', 'GET', array('a' => '1', 'b' => '2'));
+        $this->assertEquals(Test::TEST_URL . '?a=1&b=2', $test->curl->effectiveUrl);
     }
 
     public function testPostRequestMethod()
@@ -3398,4 +3389,96 @@ class CurlTest extends \PHPUnit\Framework\TestCase
             $this->assertEquals($expect_retries, $test->curl->retries);
         }
     }
+
+    public function testRelativeUrl()
+    {
+        $curl = new Curl(Test::TEST_URL . 'path/');
+        $this->assertEquals('http://127.0.0.1:8000/path/', (string)$curl->url);
+
+        $curl->get('test', array(
+            'a' => '1',
+            'b' => '2',
+        ));
+        $this->assertEquals('http://127.0.0.1:8000/path/test?a=1&b=2', (string)$curl->url);
+
+        $curl->get('/root', array(
+            'c' => '3',
+            'd' => '4',
+        ));
+        $this->assertEquals('http://127.0.0.1:8000/root?c=3&d=4', (string)$curl->url);
+
+        $tests = array(
+            array(
+                'args' => array(
+                    'http://www.example.com/',
+                    '/foo',
+                ),
+                'expected' => 'http://www.example.com/foo',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/',
+                    '/foo/',
+                ),
+                'expected' => 'http://www.example.com/foo/',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/',
+                    '/dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir/page.html',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/dir1/page2.html',
+                    '/dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir/page.html',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/dir1/page2.html',
+                    'dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir1/dir/page.html',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/dir1/dir3/page.html',
+                    '../dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir1/dir/page.html',
+            ),
+        );
+        foreach ($tests as $test) {
+            $curl = new Curl($test['args']['0']);
+            $curl->setUrl($test['args']['1']);
+            $this->assertEquals($test['expected'], $curl->getOpt(CURLOPT_URL));
+
+            $curl = new Curl($test['args']['0']);
+            $curl->setUrl($test['args']['1'], array('a' => '1', 'b' => '2'));
+            $this->assertEquals($test['expected'] . '?a=1&b=2', $curl->getOpt(CURLOPT_URL));
+
+            $curl = new Curl();
+            $curl->setUrl($test['args']['0']);
+            $curl->setUrl($test['args']['1']);
+            $this->assertEquals($test['expected'], $curl->getOpt(CURLOPT_URL));
+
+            $curl = new Curl();
+            $curl->setUrl($test['args']['0'], array('a' => '1', 'b' => '2'));
+            $curl->setUrl($test['args']['1']);
+            $this->assertEquals($test['expected'] . '?a=1&b=2', $curl->getOpt(CURLOPT_URL));
+
+            $curl = new Curl();
+            $curl->setUrl($test['args']['0']);
+            $curl->setUrl($test['args']['1'], array('a' => '1', 'b' => '2'));
+            $this->assertEquals($test['expected'] . '?a=1&b=2', $curl->getOpt(CURLOPT_URL));
+
+            $curl = new Curl();
+            $curl->setUrl($test['args']['0'], array('a' => '1', 'b' => '2'));
+            $curl->setUrl($test['args']['1'], array('c' => '3', 'd' => '4'));
+            $this->assertEquals($test['expected'] . '?c=3&d=4', $curl->getOpt(CURLOPT_URL));
+        }
+    }
 }
diff --git a/tests/PHPCurlClass/PHPMultiCurlClassTest.php b/tests/PHPCurlClass/PHPMultiCurlClassTest.php
index 1f248c9..2a64286 100644
--- a/tests/PHPCurlClass/PHPMultiCurlClassTest.php
+++ b/tests/PHPCurlClass/PHPMultiCurlClassTest.php
@@ -2290,7 +2290,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'delete_with_body');
         $multi_curl->addDelete($data, array('wibble' => 'wubble'))->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals(
                 '{"get":{"key":"value"},"delete":{"wibble":"wubble"}}',
                 $instance->rawResponse
@@ -2301,7 +2300,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'get');
         $multi_curl->addDelete($data)->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals('key=value', $instance->response);
         });
         $multi_curl->start();
@@ -2309,7 +2307,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'get');
         $multi_curl->addGet($data)->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals('key=value', $instance->response);
         });
         $multi_curl->start();
@@ -2317,7 +2314,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'get');
         $multi_curl->addHead($data)->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals(
                 'HEAD /?key=value HTTP/1.1',
                 $instance->requestHeaders['Request-Line']
@@ -2328,7 +2324,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'get');
         $multi_curl->addOptions($data)->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals('key=value', $instance->response);
         });
         $multi_curl->start();
@@ -2336,7 +2331,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'request_method');
         $multi_curl->addPatch($data)->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals('PATCH', $instance->response);
         });
         $multi_curl->start();
@@ -2344,7 +2338,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'post');
         $multi_curl->addPost($data)->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals('key=value', $instance->response);
         });
         $multi_curl->start();
@@ -2352,7 +2345,6 @@ class MultiCurlTest extends \PHPUnit\Framework\TestCase
         $multi_curl = new MultiCurl(Test::TEST_URL);
         $multi_curl->setHeader('X-DEBUG-TEST', 'put');
         $multi_curl->addPut($data)->complete(function ($instance) {
-            \PHPUnit\Framework\Assert::assertEquals(Test::TEST_URL, $instance->baseUrl);
             \PHPUnit\Framework\Assert::assertEquals('key=value', $instance->response);
         });
         $multi_curl->start();
diff --git a/tests/PHPCurlClass/UrlTest.php b/tests/PHPCurlClass/UrlTest.php
new file mode 100644
index 0000000..bd5dacd
--- /dev/null
+++ b/tests/PHPCurlClass/UrlTest.php
@@ -0,0 +1,111 @@
+<?php
+
+namespace CurlTest;
+
+use \Curl\Url;
+
+class UrlTest extends \PHPUnit\Framework\TestCase
+{
+    public function testUrlPaths()
+    {
+        $tests = array(
+            array(
+                'args' => array(
+                    'http://www.example.com/',
+                    '/foo',
+                ),
+                'expected' => 'http://www.example.com/foo',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/',
+                    '/foo/',
+                ),
+                'expected' => 'http://www.example.com/foo/',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/',
+                    '/dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir/page.html',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/dir1/page2.html',
+                    '/dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir/page.html',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/dir1/page2.html',
+                    'dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir1/dir/page.html',
+            ),
+            array(
+                'args' => array(
+                    'http://www.example.com/dir1/dir3/page.html',
+                    '../dir/page.html',
+                ),
+                'expected' => 'http://www.example.com/dir1/dir/page.html',
+            ),
+        );
+        foreach ($tests as $test) {
+            $reflector = new \ReflectionClass('\Curl\Url');
+            $url = $reflector->newInstanceArgs($test['args']);
+            $actual_url = (string)$url;
+            $this->assertEquals($test['expected'], $actual_url);
+        }
+    }
+
+    public function testUrlInstances()
+    {
+        $a = new Url('https://developer.mozilla.org', '/');
+        $this->assertEquals('https://developer.mozilla.org/', $a);
+
+        $b = new Url('https://developer.mozilla.org');
+        $this->assertEquals('https://developer.mozilla.org/', $b);
+
+        $c = new Url($b, 'en-US/docs');
+        $this->assertEquals('https://developer.mozilla.org/en-US/docs', $c);
+
+        $d = new Url($b, '/en-US/docs');
+        $this->assertEquals('https://developer.mozilla.org/en-US/docs', $d);
+
+        $f = new Url($d, '/en-US/docs');
+        $this->assertEquals('https://developer.mozilla.org/en-US/docs', $f);
+
+        $g = new Url('https://developer.mozilla.org/fr-FR/toto', '/en-US/docs');
+        $this->assertEquals('https://developer.mozilla.org/en-US/docs', $g);
+
+        $h = new Url($a, '/en-US/docs');
+        $this->assertEquals('https://developer.mozilla.org/en-US/docs', $h);
+
+        $k = new Url('https://developers.mozilla.com', 'http://www.example.com');
+        $this->assertEquals('http://www.example.com/', $k);
+
+        $l = new Url($b, 'http://www.example.com');
+        $this->assertEquals('http://www.example.com/', $l);
+    }
+
+    public function testRemoveDotSegments()
+    {
+        // TODO: Add tests using "Normal Examples" and "Abnormal Examples" from RFC 3986.
+        $tests = array(
+            array(
+                'path' => '/a/b/c/./../../g',
+                'expected' => '/a/g',
+            ),
+            array(
+                'path' => 'mid/content=5/../6',
+                'expected' => 'mid/6',
+            ),
+        );
+        foreach ($tests as $test) {
+            $actual_path = Url::removeDotSegments($test['path']);
+            $this->assertEquals($test['expected'], $actual_path);
+        }
+    }
+}