1 files changed, 122 insertions, 0 deletions
diff --git a/tools/profiler/tests/xpcshell/test_feature_mainthreadio.js b/tools/profiler/tests/xpcshell/test_feature_mainthreadio.js
new file mode 100644
index 0000000000..8ff5c9206d
--- /dev/null
+++ b/tools/profiler/tests/xpcshell/test_feature_mainthreadio.js
@@ -0,0 +1,122 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+
+/**
+ * Test that the IOInterposer is working correctly to capture main thread IO.
+ *
+ * This test should not run on release or beta, as the IOInterposer is wrapped in
+ * an ifdef.
+ */
+add_task(async () => {
+  {
+    const filename = "profiler-mainthreadio-test-firstrun";
+    const { markers, schema } = await runProfilerWithFileIO(
+      ["mainthreadio"],
+      filename
+    );
+    info("Check the FileIO markers when using the mainthreadio feature");
+    checkInflatedFileIOMarkers(markers, filename);
+
+    checkSchema(schema, {
+      name: "FileIO",
+      display: ["marker-chart", "marker-table", "timeline-fileio"],
+      data: [
+        {
+          key: "operation",
+          label: "Operation",
+          format: "string",
+          searchable: true,
+        },
+        { key: "source", label: "Source", format: "string", searchable: true },
+        {
+          key: "filename",
+          label: "Filename",
+          format: "file-path",
+          searchable: true,
+        },
+        {
+          key: "threadId",
+          label: "Thread ID",
+          format: "string",
+          searchable: true,
+        },
+      ],
+    });
+  }
+
+  {
+    const filename = "profiler-mainthreadio-test-no-instrumentation";
+    const { markers } = await runProfilerWithFileIO([], filename);
+    equal(
+      markers.length,
+      0,
+      "No FileIO markers are found when the mainthreadio feature is not turned on " +
+        "in the profiler."
+    );
+  }
+
+  {
+    const filename = "profiler-mainthreadio-test-secondrun";
+    const { markers } = await runProfilerWithFileIO(["mainthreadio"], filename);
+    info("Check the FileIO markers when re-starting the mainthreadio feature");
+    checkInflatedFileIOMarkers(markers, filename);
+  }
+});
+
+/**
+ * Start the profiler and get FileIO markers and schema.
+ *
+ * @param {Array} features The list of profiler features
+ * @param {string} filename A filename to trigger a write operation
+ * @returns {{
+ *   markers: InflatedMarkers[];
+ *   schema: MarkerSchema;
+ * }}
+ */
+async function runProfilerWithFileIO(features, filename) {
+  const entries = 10000;
+  const interval = 10;
+  const threads = [];
+  await Services.profiler.StartProfiler(entries, interval, features, threads);
+
+  info("Get the file");
+  const file = FileUtils.getFile("TmpD", [filename]);
+  if (file.exists()) {
+    console.warn(
+      "This test is triggering FileIO by writing to a file. However, the test found an " +
+        "existing file at the location it was trying to write to. This could happen " +
+        "because a previous run of the test failed to clean up after itself. This test " +
+        " will now clean up that file before running the test again."
+    );
+    file.remove(false);
+  }
+
+  info(
+    "Generate file IO on the main thread using FileUtils.openSafeFileOutputStream."
+  );
+  const outputStream = FileUtils.openSafeFileOutputStream(file);
+
+  const data = "Test data.";
+  info("Write to the file");
+  outputStream.write(data, data.length);
+
+  info("Close the file");
+  FileUtils.closeSafeFileOutputStream(outputStream);
+
+  info("Remove the file");
+  file.remove(false);
+
+  const profile = await stopNowAndGetProfile();
+  const mainThread = profile.threads.find(({ name }) => name === "GeckoMain");
+
+  const schema = getSchema(profile, "FileIO");
+
+  const markers = getInflatedFileIOMarkers(mainThread, filename);
+
+  return { schema, markers };
+}