diff --git a/web-bundle/subresource-loading/script-replace.https.tentative.html b/web-bundle/subresource-loading/script-replace.https.tentative.html
new file mode 100644
index 00000000000000..0c464b75fa5ff7
--- /dev/null
+++ b/web-bundle/subresource-loading/script-replace.https.tentative.html
@@ -0,0 +1,44 @@
+<!DOCTYPE html>
+<title>Subresource loading with script-based API</title>
+<link
+  rel="help"
+  href="https://github.com/WICG/webpackage/blob/main/explainers/subresource-loading.md"
+/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<body>
+  <script id="old_script" type="webbundle">
+    {
+      "source": "../resources/wbn/subresource.wbn",
+      "resources": ["../resources/wbn/root.js", "../resources/wbn/old-wbn.js"]
+    }
+  </script>
+  <script>
+    promise_test(async () => {
+      const old_script = document.querySelector("#old_script");
+
+      assert_true((await fetch(
+        "https://web-platform.test:8444/web-bundle/resources/wbn/root.js"
+      )).ok);
+      assert_false((await fetch(
+        "https://web-platform.test:8444/web-bundle/resources/wbn/submodule.js"
+      )).ok);
+
+      const new_script = document.createElement("script");
+      new_script.type = "webbundle";
+      new_script.textContent = JSON.stringify({
+        source: "../resources/wbn/subresource.wbn",
+        resources: ["../resources/wbn/submodule.js", "../resources/wbn/new-wbn.js"],
+      });
+
+      old_script.replaceWith(new_script);
+
+      assert_false((await fetch(
+        "https://web-platform.test:8444/web-bundle/resources/wbn/root.js"
+      )).ok);
+      assert_true((await fetch(
+        "https://web-platform.test:8444/web-bundle/resources/wbn/submodule.js"
+      )).ok);
+    }, "Subresource should be loaded from webbundle");
+  </script>
+</body>
diff --git a/web-bundle/subresource-loading/script-subresource-load.https.tentative.html b/web-bundle/subresource-loading/script-subresource-load.https.tentative.html
new file mode 100644
index 00000000000000..98c3ee5b36f30b
--- /dev/null
+++ b/web-bundle/subresource-loading/script-subresource-load.https.tentative.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<title>Subresource loading with script-based API</title>
+<link rel="help" href="https://github.com/WICG/webpackage/blob/main/explainers/subresource-loading.md" />
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<body>
+  <script type="webbundle">
+    {
+      "source": "../resources/wbn/subresource.wbn",
+      "resources": ["../resources/wbn/root.js"]
+    }
+  </script>
+    <script>
+      promise_test(async () => {
+        const response = await fetch('https://web-platform.test:8444/web-bundle/resources/wbn/root.js');
+        assert_true(response.ok);
+      }, "Subresource should be loaded from webbundle");
+  </script>
+</body>
diff --git a/web-bundle/subresource-loading/script-supports-webbundle.https.tentative.html b/web-bundle/subresource-loading/script-supports-webbundle.https.tentative.html
new file mode 100644
index 00000000000000..f0aabf5d565331
--- /dev/null
+++ b/web-bundle/subresource-loading/script-supports-webbundle.https.tentative.html
@@ -0,0 +1,15 @@
+<DOCTYPE html>
+<html>
+<title>HTMLScriptElement.supports webbundle</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(() => {
+  assert_true(HTMLScriptElement.supports('webbundle'));
+}, 'HTMLScriptElement.supports returns true for \'webbundle\'');
+
+test(() => {
+  assert_false(HTMLScriptElement.supports(' webbundle'));
+  assert_false(HTMLScriptElement.supports('webbundle '));
+}, 'HTMLScriptElement.supports returns false for unsupported types');
+</script>
