1 files changed, 64 insertions, 0 deletions
diff --git a/testing/web-platform/tests/compression/compression-output-length.tentative.any.js b/testing/web-platform/tests/compression/compression-output-length.tentative.any.js
new file mode 100644
index 0000000000..07efe92a82
--- /dev/null
+++ b/testing/web-platform/tests/compression/compression-output-length.tentative.any.js
@@ -0,0 +1,64 @@
+// META: global=window,worker
+
+'use strict';
+
+// This test asserts that compressed data length is shorter than the original
+// data length. If the input is extremely small, the compressed data may be
+// larger than the original data.
+
+const LARGE_FILE = '/media/test-av-384k-44100Hz-1ch-320x240-30fps-10kfr.webm';
+
+async function compressArrayBuffer(input, format) {
+  const cs = new CompressionStream(format);
+  const writer = cs.writable.getWriter();
+  writer.write(input);
+  const closePromise = writer.close();
+  const out = [];
+  const reader = cs.readable.getReader();
+  let totalSize = 0;
+  while (true) {
+    const { value, done } = await reader.read();
+    if (done)
+      break;
+    out.push(value);
+    totalSize += value.byteLength;
+  }
+  await closePromise;
+  const concatenated = new Uint8Array(totalSize);
+  let offset = 0;
+  for (const array of out) {
+    concatenated.set(array, offset);
+    offset += array.byteLength;
+  }
+  return concatenated;
+}
+
+promise_test(async () => {
+  const response = await fetch(LARGE_FILE);
+  const buffer = await response.arrayBuffer();
+  const bufferView = new Uint8Array(buffer);
+  const originalLength = bufferView.length;
+  const compressedData = await compressArrayBuffer(bufferView, 'deflate');
+  const compressedLength = compressedData.length;
+  assert_less_than(compressedLength, originalLength, 'output should be smaller');
+}, 'the length of deflated data should be shorter than that of the original data');
+
+promise_test(async () => {
+  const response = await fetch(LARGE_FILE);
+  const buffer = await response.arrayBuffer();
+  const bufferView = new Uint8Array(buffer);
+  const originalLength = bufferView.length;
+  const compressedData = await compressArrayBuffer(bufferView, 'gzip');
+  const compressedLength = compressedData.length;
+  assert_less_than(compressedLength, originalLength, 'output should be smaller');
+}, 'the length of gzipped data should be shorter than that of the original data');
+
+promise_test(async () => {
+  const response = await fetch(LARGE_FILE);
+  const buffer = await response.arrayBuffer();
+  const bufferView = new Uint8Array(buffer);
+  const originalLength = bufferView.length;
+  const compressedData = await compressArrayBuffer(bufferView, 'deflate-raw');
+  const compressedLength = compressedData.length;
+  assert_less_than(compressedLength, originalLength, 'output should be smaller');
+}, 'the length of deflated (with -raw) data should be shorter than that of the original data');