diff --git a/plugins/techdocs/src/reader/transformers/html/transformer.test.tsx b/plugins/techdocs/src/reader/transformers/html/transformer.test.tsx
new file mode 100644
index 0000000000..ab64eccaa4
--- /dev/null
+++ b/plugins/techdocs/src/reader/transformers/html/transformer.test.tsx
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import React, { FC } from 'react';
+import { renderHook } from '@testing-library/react-hooks';
+
+import { ConfigReader } from '@backstage/core-app-api';
+import { ConfigApi, configApiRef } from '@backstage/core-plugin-api';
+import { TestApiProvider } from '@backstage/test-utils';
+
+import { useHtmlTransformer } from './transformer';
+
+const configApiMock: ConfigApi = new ConfigReader({
+ techdocs: {
+ sanitizer: {
+ allowedIframeHosts: ['docs.google.com'],
+ },
+ },
+});
+
+const wrapper: FC = ({ children }) => (
+
+ {children}
+
+);
+
+describe('Transformers > Html', () => {
+ it('should return a function that removes unsafe links from a given dom element', async () => {
+ const { result } = renderHook(() => useHtmlTransformer(), { wrapper });
+
+ const dirtyDom = document.createElement('html');
+ dirtyDom.innerHTML = `
+
+
+
+
+
+
+ `;
+ const clearDom = await result.current(dirtyDom); // calling html transformer
+
+ const links = Array.from(
+ clearDom.querySelectorAll('head > link'),
+ );
+ expect(links).toHaveLength(3);
+ expect(links[0].href).toMatch('assets/stylesheets/main.50e68009.min.css');
+ expect(links[1].href).toMatch('https://fonts.googleapis.com');
+ expect(links[2].href).toMatch('https://fonts.gstatic.com');
+ });
+
+ it('should return a function that removes unsafe iframes from a given dom element', async () => {
+ const { result } = renderHook(() => useHtmlTransformer(), { wrapper });
+
+ const dirtyDom = document.createElement('html');
+ dirtyDom.innerHTML = `
+
+
+
+
+
+ `;
+ const clearDom = await result.current(dirtyDom); // calling html transformer
+
+ const iframes = Array.from(
+ clearDom.querySelectorAll('body > iframe'),
+ );
+
+ expect(iframes).toHaveLength(1);
+ expect(iframes[0].src).toMatch('docs.google.com');
+ });
+});