1 files changed, 65 insertions, 0 deletions
diff --git a/testing/web-platform/tests/xhr/formdata/iteration.any.js b/testing/web-platform/tests/xhr/formdata/iteration.any.js
new file mode 100644
index 0000000000..1633fd9c4d
--- /dev/null
+++ b/testing/web-platform/tests/xhr/formdata/iteration.any.js
@@ -0,0 +1,65 @@
+// META: title=FormData: changes to entry list during iteration
+
+// These are tests for next()'s behavior as specified in
+// https://webidl.spec.whatwg.org/#es-iterator-prototype-object
+
+"use strict";
+
+function createFormData(input) {
+    const formData = new FormData();
+
+    for (const [name, value] of input) {
+        formData.append(name, value);
+    }
+
+    return formData;
+}
+
+test(() => {
+    const formData = createFormData([["foo", "0"],
+                                     ["baz", "1"],
+                                     ["BAR", "2"]]);
+    const actualKeys = [];
+    const actualValues = [];
+    for (const [name, value] of formData) {
+        actualKeys.push(name);
+        actualValues.push(value);
+        formData.delete("baz");
+    }
+    assert_array_equals(actualKeys, ["foo", "BAR"]);
+    assert_array_equals(actualValues, ["0", "2"]);
+}, "Iteration skips elements removed while iterating");
+
+test(() => {
+    const formData = createFormData([["foo", "0"],
+                                     ["baz", "1"],
+                                     ["BAR", "2"],
+                                     ["quux", "3"]]);
+    const actualKeys = [];
+    const actualValues = [];
+    for (const [name, value] of formData) {
+        actualKeys.push(name);
+        actualValues.push(value);
+        if (name === "baz")
+            formData.delete("foo");
+    }
+    assert_array_equals(actualKeys, ["foo", "baz", "quux"]);
+    assert_array_equals(actualValues, ["0", "1", "3"]);
+}, "Removing elements already iterated over causes an element to be skipped during iteration");
+
+test(() => {
+    const formData = createFormData([["foo", "0"],
+                                     ["baz", "1"],
+                                     ["BAR", "2"],
+                                     ["quux", "3"]]);
+    const actualKeys = [];
+    const actualValues = [];
+    for (const [name, value] of formData) {
+        actualKeys.push(name);
+        actualValues.push(value);
+        if (name === "baz")
+            formData.append("X-yZ", "4");
+    }
+    assert_array_equals(actualKeys, ["foo", "baz", "BAR", "quux", "X-yZ"]);
+    assert_array_equals(actualValues, ["0", "1", "2", "3", "4"]);
+}, "Appending a value pair during iteration causes it to be reached during iteration");