1 files changed, 56 insertions, 0 deletions
diff --git a/packages/meshbay-hub/tests/test_downloads.py b/packages/meshbay-hub/tests/test_downloads.py
index cd0cded..41d61bf 100644
--- a/packages/meshbay-hub/tests/test_downloads.py
+++ b/packages/meshbay-hub/tests/test_downloads.py
@@ -108,3 +108,59 @@ def test_the_open_action_reads_the_file_back(tmp_path):
     target = src[src.index("export async function openTarget"):]
     assert "getFile()" in target and "window.open(" in target
     assert "revokeObjectURL" in target, "the blob URL must not be leaked"
+
+
+# ── Streaming to disk without the File System Access API ────────────────────
+
+SW = STATIC / "sw.js"
+
+
+def test_the_worker_only_answers_its_own_urls():
+    """
+    It is registered at the root scope, so it sees every request the page makes.
+    Anything that is not a download of ours has to fall through untouched — a
+    service worker that answers more than it should is a cache bug waiting to
+    happen.
+    """
+    src = SW.read_text()
+    assert "startsWith(PREFIX)" in src
+    assert "self.location.origin" in src, "cross-origin requests must fall through"
+    # The API, not the word: the file explains in prose that it caches nothing.
+    for api in ("caches.open", "caches.match", "cache.put"):
+        assert api not in src, f"this worker must not cache anything ({api})"
+
+
+def test_the_download_is_announced_as_an_attachment():
+    src = SW.read_text()
+    assert "Content-Disposition" in src and "attachment" in src
+    assert "filename*=UTF-8''" in src, "a name with accents would be mangled"
+    assert "Content-Length" in src
+
+
+def test_a_length_is_only_promised_when_it_is_known(tmp_path):
+    """
+    An archive is assembled as it goes and is larger than the files in it.
+    Announcing the sum of their sizes would truncate the download at that mark.
+    """
+    src = SW.read_text()
+    assert "if (entry.size > 0)" in src
+
+    app = (STATIC / "app.js").read_text()
+    zip_call = app[app.index("const target = await _openDownloadTarget(suggested"):]
+    zip_call = zip_call[:zip_call.index(");") + 2]
+    assert zip_call.rstrip().endswith(", 0);"), (
+        "the zip download announces a Content-Length it will not match")
+
+
+def test_backpressure_is_real(tmp_path):
+    """
+    The point of the service worker path is not holding the file. A stream that
+    is transferred gives `writer.write()` something to wait on; posting chunks
+    to a port would queue them in memory and look identical from here.
+    """
+    src = DOWNLOADS.read_text()
+    fn = src[src.index("export async function openStreamedDownload"):]
+    assert "new TransformStream()" in fn
+    assert "[readable]" in fn, "the readable half must be transferred, not copied"
+    assert "writer.write(bytes)" in fn
+    assert "return null" in fn, "a browser that cannot transfer streams must say so"