The default URLs should be relative to web root (not "FIXME").

src/BasicAssetRule.php

@@ -37,7 +37,8 @@ class BasicAssetRule extends AbstractAssetRule {
     . sprintf("\$civicrm_paths[%s][%s] = %s;\n",
       var_export($this->pathVar, 1),
       var_export('url', 1),
-      var_export('FIXME' . $this->getWebPath($publisher), 1));
+      // Common default: Relative to web root
+      var_export($this->getWebPath($publisher), 1));
   }
 
 }

tests/Integration/CustomPathsTest.php

@@ -18,7 +18,7 @@ class CustomPathsTest extends \Civi\AssetPlugin\Integration\IntegrationTestCase
       'extra' => [
         'civicrm-asset' => [
           'path' => 'htdocs/foo-civi-assets',
-          'url' => '/bar-civi-assets',
+          'url' => 'http://example.com/bar-civi-assets',
           // FIXME: Maybe custom 'files' listing as well?
         ],
       ],
@@ -67,9 +67,9 @@ class CustomPathsTest extends \Civi\AssetPlugin\Integration\IntegrationTestCase
     // The JS/CSS assets are sync'd to web dir, but the $civicrm_paths should still autoload PHP from the src folder.
     $expectPaths = [];
     $expectPaths['civicrm.root']['path'] = realpath(self::getTestDir()) . '/vendor/civicrm/civicrm-core';
-    $expectPaths['civicrm.root']['url'] = 'FIXME/bar-civi-assets/core';
+    $expectPaths['civicrm.root']['url'] = 'http://example.com/bar-civi-assets/core';
     $expectPaths['civicrm.packages']['path'] = realpath(self::getTestDir()) . '/vendor/civicrm/civicrm-packages';
-    $expectPaths['civicrm.packages']['url'] = 'FIXME/bar-civi-assets/packages';
+    $expectPaths['civicrm.packages']['url'] = 'http://example.com/bar-civi-assets/packages';
     // FIXME url checks
 
     $count = 0;

tests/Integration/DefaultPathsTest.php

@@ -57,9 +57,9 @@ class DefaultPathsTest extends \Civi\AssetPlugin\Integration\IntegrationTestCase
     // The JS/CSS assets are sync'd to web dir, but the $civicrm_paths should still autoload PHP from the src folder.
     $expectPaths = [];
     $expectPaths['civicrm.root']['path'] = realpath(self::getTestDir()) . '/vendor/civicrm/civicrm-core';
-    $expectPaths['civicrm.root']['url'] = 'FIXME/civicrm-assets/core';
+    $expectPaths['civicrm.root']['url'] = '/civicrm-assets/core';
     $expectPaths['civicrm.packages']['path'] = realpath(self::getTestDir()) . '/vendor/civicrm/civicrm-packages';
-    $expectPaths['civicrm.packages']['url'] = 'FIXME/civicrm-assets/packages';
+    $expectPaths['civicrm.packages']['url'] = '/civicrm-assets/packages';
     // FIXME url checks
 
     $count = 0;

tests/Integration/DrupalProjectPathsTest.php

@@ -76,9 +76,9 @@ class DrupalProjectPathsTest extends \Civi\AssetPlugin\Integration\IntegrationTe
     // The JS/CSS assets are sync'd to web dir, but the $civicrm_paths should still autoload PHP from the src folder.
     $expectPaths = [];
     $expectPaths['civicrm.root']['path'] = realpath(self::getTestDir()) . '/vendor/civicrm/civicrm-core';
-    $expectPaths['civicrm.root']['url'] = 'FIXME/libraries/civicrm/core';
+    $expectPaths['civicrm.root']['url'] = '/libraries/civicrm/core';
     $expectPaths['civicrm.packages']['path'] = realpath(self::getTestDir()) . '/vendor/civicrm/civicrm-packages';
-    $expectPaths['civicrm.packages']['url'] = 'FIXME/libraries/civicrm/packages';
+    $expectPaths['civicrm.packages']['url'] = '/libraries/civicrm/packages';
     // FIXME url checks
 
     $count = 0;