1 files changed, 88 insertions, 0 deletions
diff --git a/services/common/tests/unit/test_async_foreach.js b/services/common/tests/unit/test_async_foreach.js
new file mode 100644
index 0000000000..14a23e7ff7
--- /dev/null
+++ b/services/common/tests/unit/test_async_foreach.js
@@ -0,0 +1,88 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Async } = ChromeUtils.importESModule(
+  "resource://services-common/async.sys.mjs"
+);
+const { sinon } = ChromeUtils.importESModule(
+  "resource://testing-common/Sinon.sys.mjs"
+);
+
+function makeArray(length) {
+  // Start at 1 so that we can just divide by yieldEvery to get the expected
+  // call count. (we exp)
+  return Array.from({ length }, (v, i) => i + 1);
+}
+
+// Adjust if we ever change the default.
+const DEFAULT_YIELD_EVERY = 50;
+
+add_task(async function testYields() {
+  let spy = sinon.spy(Async, "promiseYield");
+  try {
+    await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY * 2), element => {
+      // The yield will happen *after* this function is ran.
+      Assert.equal(
+        spy.callCount,
+        Math.floor((element - 1) / DEFAULT_YIELD_EVERY)
+      );
+    });
+  } finally {
+    spy.restore();
+  }
+});
+
+add_task(async function testExistingYieldState() {
+  const yieldState = Async.yieldState(DEFAULT_YIELD_EVERY);
+
+  for (let i = 0; i < 15; i++) {
+    Assert.equal(yieldState.shouldYield(), false);
+  }
+
+  let spy = sinon.spy(Async, "promiseYield");
+
+  try {
+    await Async.yieldingForEach(
+      makeArray(DEFAULT_YIELD_EVERY * 2),
+      element => {
+        Assert.equal(
+          spy.callCount,
+          Math.floor((element + 15 - 1) / DEFAULT_YIELD_EVERY)
+        );
+      },
+      yieldState
+    );
+  } finally {
+    spy.restore();
+  }
+});
+
+add_task(async function testEarlyReturn() {
+  let lastElement = 0;
+  await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY), element => {
+    lastElement = element;
+    return element === 10;
+  });
+
+  Assert.equal(lastElement, 10);
+});
+
+add_task(async function testEaryReturnAsync() {
+  let lastElement = 0;
+  await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY), async element => {
+    lastElement = element;
+    return element === 10;
+  });
+
+  Assert.equal(lastElement, 10);
+});
+
+add_task(async function testEarlyReturnPromise() {
+  let lastElement = 0;
+  await Async.yieldingForEach(makeArray(DEFAULT_YIELD_EVERY), element => {
+    lastElement = element;
+    return new Promise(resolve => resolve(element === 10));
+  });
+
+  Assert.equal(lastElement, 10);
+});