vs/add test to verify .mp3 naming extension. (#1051)

Author: vsangereanMOZ

manifests/key.yaml

@@ -387,6 +387,10 @@ downloads:
     result: pass
     splits:
     - functional1
+  test_download_mp3_and_check_extension:
+    result: pass
+    splits:
+    - functional1
   test_download_pdf:
     result: pass
     splits:

tests/downloads/test_download_mp3_and_check_extension.py

@@ -0,0 +1,47 @@
+import pytest
+from selenium.webdriver import Firefox
+
+from modules.browser_object_navigation import Navigation
+from modules.page_object_generics import GenericPage
+
+MP3_URL = "https://download.samplelib.com/mp3/sample-3s.mp3"
+MP3_NAME_REGEX = r".*\.mp3(\s\(\d+\))?$"
+
+
+@pytest.fixture()
+def test_case():
+    return "1836832"
+
+
+@pytest.mark.headed
+def test_download_mp3_and_check_extension(driver: Firefox):
+    """
+    1836829: Verify the mp3 filename shown in Firefox Downloads panel includes `.mp3`
+    """
+    nav = Navigation(driver)
+
+    # Load a normal page
+    page = GenericPage(driver, url="about:blank")
+    page.open()
+
+    # Simulate downloading the file by creating and clicking an anchor element
+    driver.execute_script(
+        """
+        const a = document.createElement("a");
+        a.href = arguments[0];
+        a.click();
+    """,
+        MP3_URL,
+    )
+
+    # Dismiss "harmful file" warning if present
+    try:
+        nav.click_file_download_warning_panel()
+    except Exception:
+        pass
+
+    # Wait for the download entry in the panel
+    nav.element_visible("download-target-element")
+
+    # Reuse the verification that already worked
+    nav.verify_download_name(MP3_NAME_REGEX)