diff --git a/html/semantics/scripting-1/the-script-element/css-module/css-module-worker-test.html b/html/semantics/scripting-1/the-script-element/css-module/css-module-worker-test.html
new file mode 100644
index 000000000000000..8938d1676c3deaa
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/css-module-worker-test.html
@@ -0,0 +1,37 @@
+<!doctype html>
+
+<head>
+    <title>import-css-module-worker</title>
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+</head>
+
+<body>
+    <h1>import-css-module-worker</h1>
+    <script>
+        async_test(function (test) {
+            const worker = new Worker("./resources/worker.js", {
+                type: "module"
+            });
+            worker.onmessage = test.step_func(() => {
+                assert_unreached(
+                    "A CSS Module within a web worker should not load.")
+            });
+            worker.onerror = test.step_func_done();
+        }, "A CSS Module within a web worker should not load.");
+    </script>
+
+    <script>
+        async_test(function (test) {
+            const worker = new Worker("./resources/worker_dynamic_import.js", {
+                type: "module"
+            });
+            worker.onmessage = test.step_func(() => {
+                assert_unreached(
+                    "A dynamic import CSS Module within a web worker should not load.")
+            });
+            worker.onerror = test.step_func_done();
+        }, "A dynamic import CSS Module within a web worker should not load.");
+    </script>
+
+</body>
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/import-css-module-basic.html b/html/semantics/scripting-1/the-script-element/css-module/import-css-module-basic.html
new file mode 100644
index 000000000000000..865950066523cf6
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/import-css-module-basic.html
@@ -0,0 +1,52 @@
+<!doctype html>
+
+<head>
+    <title>import-css-module-basic</title>
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+</head>
+
+<body>
+    <h1>import-css-module-basic</h1>
+    <script type="module">
+        import v from "./resources/basic.css";
+        document.adoptedStyleSheets = [v];
+        test(function () {
+            assert_equals(getComputedStyle(document.querySelector('#test'))
+                .backgroundColor, "rgb(255, 0, 0)",
+                "CSS module should import correctly on top level document");
+        }, "Test basic CSS module import");
+    </script>
+
+    <script type="module">
+        async_test(function (test) {
+            let iframe = document.createElement("iframe");
+            iframe.src = "resources/css_module_at_import_iframe.html";
+            iframe.onload = test.step_func_done(function () {
+                assert_equals(iframe.contentDocument.load_error, "NotAllowedError");
+                assert_not_equals(getComputedStyle(iframe.contentDocument.querySelector('#test'))
+                    .backgroundColor, "rgb(255, 0, 0)",
+                    "CSS module @import should not succeed");
+            });
+            document.body.appendChild(iframe);
+        }, "An @import CSS Module should not load");
+    </script>
+
+    <script type="module">
+        async_test(function (test) {
+            let iframe = document.createElement("iframe");
+            iframe.src = "resources/malformed.html";
+            iframe.onload = test.step_func_done(function () {
+                assert_equals(iframe.contentDocument.load_error, "ParseError");
+                assert_not_equals(getComputedStyle(iframe.contentDocument.querySelector('#test'))
+                    .backgroundColor, "rgb(255, 0, 0)",
+                    "Malformed CSS should throw parse error");
+            });
+            document.body.appendChild(iframe);
+        }, "Malformed CSS should throw parse error");
+    </script>
+
+    <div id="test">
+        I am a test div.
+    </div>
+</body>
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/resources/bad_import.css b/html/semantics/scripting-1/the-script-element/css-module/resources/bad_import.css
new file mode 100644
index 000000000000000..796446b525ca03b
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/resources/bad_import.css
@@ -0,0 +1 @@
+@import "basic.css"
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/resources/basic.css b/html/semantics/scripting-1/the-script-element/css-module/resources/basic.css
new file mode 100644
index 000000000000000..3ea2ef45339c41d
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/resources/basic.css
@@ -0,0 +1,3 @@
+#test {
+    background-color:red;
+}
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/resources/css_module_at_import_iframe.html b/html/semantics/scripting-1/the-script-element/css-module/resources/css_module_at_import_iframe.html
new file mode 100644
index 000000000000000..9f50cf01a9fa309
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/resources/css_module_at_import_iframe.html
@@ -0,0 +1,18 @@
+<body>
+    css-module-at-import
+    <script>
+        window.onerror = function (errorMsg, url, lineNumber, column, errorObj)
+        {
+            document.load_error = errorObj.name;
+            return true;
+        };
+    </script>
+    <script type="module">
+        import v from "./bad_import.css";
+        document.adoptedStyleSheets = [v];
+    </script>
+
+    <div id="test">
+        I am a test div.
+    </div>
+</body>
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/resources/malformed.css b/html/semantics/scripting-1/the-script-element/css-module/resources/malformed.css
new file mode 100644
index 000000000000000..fb20336584e7745
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/resources/malformed.css
@@ -0,0 +1,3 @@
+#test {{
+    background-color:red;
+}
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/resources/worker.js b/html/semantics/scripting-1/the-script-element/css-module/resources/worker.js
new file mode 100644
index 000000000000000..8997ae45102bb54
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/resources/worker.js
@@ -0,0 +1 @@
+import "./basic.css";
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/resources/worker_dynamic_import.js b/html/semantics/scripting-1/the-script-element/css-module/resources/worker_dynamic_import.js
new file mode 100644
index 000000000000000..796446b525ca03b
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/resources/worker_dynamic_import.js
@@ -0,0 +1 @@
+@import "basic.css"
\ No newline at end of file
diff --git a/html/semantics/scripting-1/the-script-element/css-module/utf8.tentative.html b/html/semantics/scripting-1/the-script-element/css-module/utf8.tentative.html
new file mode 100644
index 000000000000000..e190bb2414955b7
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/utf8.tentative.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<meta charset=utf-8>
+<title>CSS modules: UTF-8 decoding</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id=log></div>
+<script>
+function check(t, v) {
+  t.step(() => {
+    assert_equals(typeof v, "object");
+    assert_array_equals(Object.keys(v), ["test"]);
+    assert_equals(v.test, "\u2026");
+    t.done();
+  });
+}
+const t1 = async_test("utf-8");
+const t2 = async_test("shift-jis");
+const t3 = async_test("windows-1252");
+const t4 = async_test("utf-7");
+</script>
+<script type="module" onerror="t1.step(() => assert_unreached(event))">
+import v from "../serve-with-content-type.py?fn=css-module/resources/basic.css&ct=text/css%3Bcharset=utf-8";
+check(t1, v);
+</script>
+<script type="module" onerror="t2.step(() => assert_unreached(event))">
+import v from "../serve-with-content-type.py?fn=css-module/resources/basic.css&ct=text/css%3Bcharset=shift-jis";
+check(t2, v);
+</script>
+<script type="module" onerror="t3.step(() => assert_unreached(event))">
+import v from "../serve-with-content-type.py?fn=css-module/resources/basic.css&ct=text/css%3Bcharset=windows-1252";
+check(t3, v);
+</script>
+<script type="module" onerror="t4.step(() => assert_unreached(event))">
+import v from "../serve-with-content-type.py?fn=css-module/resources/basic.css&ct=text/css%3Bcharset=utf-7";
+check(t4, v);
+</script>
diff --git a/html/semantics/scripting-1/the-script-element/css-module/valid-content-type.tentative.html b/html/semantics/scripting-1/the-script-element/css-module/valid-content-type.tentative.html
new file mode 100644
index 000000000000000..17670cf50560927
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/css-module/valid-content-type.tentative.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<meta charset=utf-8>
+<title>JSON modules: Content-Type</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id=log></div>
+<script>
+function check(t, v) {
+  t.step(() => {
+    assert_equals(typeof v, "object");
+    assert_array_equals(Object.keys(v), ["test"]);
+    assert_equals(v.test, true);
+    t.done();
+  });
+}
+const t1 = async_test("text/css");
+</script>
+<script type="module" onerror="t1.step(() => assert_unreached(event))">
+import v from "../serve-with-content-type.py?fn=css-module/resources/basic.css&ct=text/css";
+check(t1, v);
+</script>
\ No newline at end of file
