diff --git a/testing/mochitest/runtests.py b/testing/mochitest/runtests.py
index 43f87506954d..0d06a8a64c70 100644
--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -144,11 +144,12 @@ class MessageLogger(object):
             "buffering_off",
         ]
     )
+    # Regexes that will be replaced with an empty string if found in a test
+    # name. We do this to normalize test names which may contain URLs and test
+    # package prefixes.
     TEST_PATH_PREFIXES = [
-        "/tests/",
-        "chrome://mochitests/content/a11y/",
-        "chrome://mochitests/content/browser/",
-        "chrome://mochitests/content/chrome/",
+        r"^/tests/",
+        r"^\w+://[\w\.]+(:\d+)?(/\w+)?/(tests?|a11y|chrome|browser)/",
     ]
 
     def __init__(self, logger, buffering=True, structured=True):
@@ -190,9 +191,10 @@ class MessageLogger(object):
         """Normalize a logged test path to match the relative path from the sourcedir."""
         if message.get("test") is not None:
             test = message["test"]
-            for prefix in MessageLogger.TEST_PATH_PREFIXES:
-                if test.startswith(prefix):
-                    message["test"] = test[len(prefix) :]
+            for pattern in MessageLogger.TEST_PATH_PREFIXES:
+                test = re.sub(pattern, "", test)
+                if test != message["test"]:
+                    message["test"] = test
                     break
 
     def _fix_message_format(self, message):
diff --git a/testing/mochitest/tests/python/test_message_logger.py b/testing/mochitest/tests/python/test_message_logger.py
index 65b2c9618447..2654089d2778 100644
--- a/testing/mochitest/tests/python/test_message_logger.py
+++ b/testing/mochitest/tests/python/test_message_logger.py
@@ -53,7 +53,7 @@ def get_message_logger(setup_test_harness, logger):
             message["message"] = "foobar"
 
         message.update(**extra)
-        return self.process_message(message)
+        return self.write(json.dumps(message))
 
     def inner(**kwargs):
         ml = runtests.MessageLogger(logger, **kwargs)
@@ -66,22 +66,31 @@ def get_message_logger(setup_test_harness, logger):
 
 
 @pytest.fixture
-def assert_actions(logger):
+def get_lines(logger):
     buf = logger.handlers[0].stream
 
-    def inner(expected):
-        if isinstance(expected, string_types):
-            expected = [expected]
-
+    def inner():
         lines = buf.getvalue().splitlines()
-        actions = [json.loads(l)["action"] for l in lines]
-        assert actions == expected
         buf.truncate(0)
         # Python3 will not reposition the buffer position after
         # truncate and will extend the buffer with null bytes.
         # Force the buffer position to the start of the buffer
         # to prevent null bytes from creeping in.
         buf.seek(0)
+        return lines
+
+    return inner
+
+
+@pytest.fixture
+def assert_actions(get_lines):
+    def inner(expected):
+        if isinstance(expected, string_types):
+            expected = [expected]
+
+        lines = get_lines()
+        actions = [json.loads(l)["action"] for l in lines]
+        assert actions == expected
 
     return inner
 
@@ -155,5 +164,30 @@ def test_buffering_off(get_message_logger, assert_actions):
     assert_actions(["test_end"])
 
 
+@pytest.mark.parametrize(
+    "name,expected",
+    (
+        ("/tests/test_foo.html", "test_foo.html"),
+        ("chrome://mochitests/content/a11y/test_foo.html", "test_foo.html"),
+        ("chrome://mochitests/content/browser/test_foo.html", "test_foo.html"),
+        ("chrome://mochitests/content/chrome/test_foo.html", "test_foo.html"),
+        (
+            "https://example.org:443/tests/netwerk/test_foo.html",
+            "netwerk/test_foo.html",
+        ),
+        ("http://mochi.test:8888/tests/test_foo.html", "test_foo.html"),
+        ("http://mochi.test:8888/content/dom/browser/test_foo.html", None),
+    ),
+)
+def test_test_names_fixed_to_be_relative(name, expected, get_message_logger, get_lines):
+    ml = get_message_logger(buffering=False)
+    ml.fake_message("test_start", test=name)
+    lines = get_lines()
+
+    if expected is None:
+        expected = name
+    assert json.loads(lines[0])["test"] == expected
+
+
 if __name__ == "__main__":
     mozunit.main()