1 files changed, 43 insertions, 0 deletions
diff --git a/dom/fs/test/common/test_writableFileStream.js b/dom/fs/test/common/test_writableFileStream.js
new file mode 100644
index 0000000000..7ddf553533
--- /dev/null
+++ b/dom/fs/test/common/test_writableFileStream.js
@@ -0,0 +1,43 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const allowCreate = { create: true };
+
+exported_symbols.test0 = async function() {
+  let root = await navigator.storage.getDirectory();
+  Assert.ok(!!root, "Can we access the root directory?");
+
+  const testFile = await root.getFileHandle("test.txt", allowCreate);
+  Assert.ok(!!testFile, "Can't access existing file");
+  let writable = await testFile.createWritable();
+  Assert.ok(!!writable, "Can't create WritableFileStream to existing file");
+
+  // Write a sentence to the end of the file.
+  const encoder = new TextEncoder();
+  const writeBuffer = encoder.encode("Thank you for reading this.");
+  try {
+    dump("Trying to write...\n");
+    await writable.write(writeBuffer);
+    dump("closing...\n");
+    await writable.close();
+  } catch (e) {
+    Assert.ok(false, "Couldn't write to WritableFileStream: " + e);
+  }
+
+  // Read it back
+  // Get size of the file.
+  let file = await testFile.getFile();
+  Assert.ok(
+    !!file,
+    "Can't create File to file written with WritableFileStream"
+  );
+  let fileSize = file.size;
+  Assert.ok(fileSize == writeBuffer.byteLength);
+};
+
+for (const [key, value] of Object.entries(exported_symbols)) {
+  Object.defineProperty(value, "name", {
+    value: key,
+    writable: false,
+  });
+}