diff --git a/packages/assemble-lite/Assemble.js b/packages/assemble-lite/Assemble.js
index a55d119..fc3a657 100644
--- a/packages/assemble-lite/Assemble.js
+++ b/packages/assemble-lite/Assemble.js
@@ -1,5 +1,7 @@
 const { basename, relative, dirname, extname } = require("path");
+const { promisify } = require("util");
 const { readJson, readFile } = require("fs-extra");
+const fsExtra = require("fs-extra");
 const pvHandlebars = require("handlebars").create();
 const { loadFront } = require("yaml-front-matter");
 const handlebarsHelpers = require("handlebars-helpers/lib/index");
@@ -7,12 +9,7 @@ const { load } = require("js-yaml");
 
 const Timer = require("./Timer");
 const Visitor = require("./Visitor");
-const {
-  getPaths,
-  asyncReadFile,
-  asyncWriteFile,
-  getName,
-} = require("./helper/io-helper");
+const { getPaths, asyncReadFile, getName } = require("./helper/io-helper");
 
 /**
  * provides an instance which build html pages from handlebars templates, helpers and data
@@ -40,6 +37,7 @@ module.exports = class Assemble {
     // it helps the user to not forget to fix stuff,
     // and sometimes a simple re-run might help. e.g. when there was a i/o issues
     this.failedPaths = [];
+    this.fs = fsExtra;
   }
 
   // console logs in verbose mode
@@ -439,7 +437,8 @@ module.exports = class Assemble {
       // only write to disc when the value changes
       if (html !== tpl.output)
         writingJobs.push(
-          asyncWriteFile(componentsTargetDirectory, reldir, filename, html)
+          // eslint-disable-next-line prettier/prettier
+          this._asyncWriteFile(componentsTargetDirectory, reldir, filename, html)
         );
 
       tpl.output = html;
@@ -453,7 +452,8 @@ module.exports = class Assemble {
         ? this.layouts[tpl.layout].render({ ...curData, __body__: body })
         : body;
       if (html !== tpl.output)
-        await asyncWriteFile(pagesTargetDirectory, reldir, filename, html);
+        // eslint-disable-next-line prettier/prettier
+        await this._asyncWriteFile(pagesTargetDirectory, reldir, filename, html);
       tpl.output = html;
     }
   }
@@ -633,4 +633,11 @@ module.exports = class Assemble {
         delete obj[key];
       });
   }
+
+  // writes to the content to the file system. depending on the setup this might be the real file system or one in memory.
+  async _asyncWriteFile(target, reldir, filename, markup) {
+    await promisify(this.fs.mkdir)(`${target}/${reldir}`, { recursive: true });
+    // eslint-disable-next-line prettier/prettier
+    await promisify(this.fs.writeFile)(`${target}/${reldir}/${filename}.html`, markup);
+  }
 };
diff --git a/packages/pv-stylemark/helper/io-helper.js b/packages/pv-stylemark/helper/io-helper.js
index 5a5a4af..0d0a94b 100644
--- a/packages/pv-stylemark/helper/io-helper.js
+++ b/packages/pv-stylemark/helper/io-helper.js
@@ -1,12 +1,20 @@
-const { ensureDir, writeFile: fsWriteFile, watchFile } = require("fs-extra");
+let fs = require("fs-extra");
+const { promisify } = require("util");
 const { glob } = require("glob");
 const { resolve, normalize } = require("path");
 
+// can override the filesystem api used to read and write files, e.g. using memfs via webpack.
+function updateFileSystemConnector(fileSystem) {
+  fs = fileSystem;
+}
+
+function readFile(...args) {
+  return promisify(fs.readFile)(...args);
+}
+
 const writeFile = async (target, reldir, filename, markup) => {
-  await ensureDir(`${target}/${reldir}`);
-  return await fsWriteFile(`${target}/${reldir}/${filename}.html`, markup, {
-    encoding: "utf8",
-  });
+  await promisify(fs.mkdir)(`${target}/${reldir}`, { recursive: true });
+  return promisify(fs.writeFile)(`${target}/${reldir}/${filename}.html`, markup);
 };
 
 const watchGlob = async (curGlob, callback) => {
@@ -15,11 +23,13 @@ const watchGlob = async (curGlob, callback) => {
   });
   const normalizedPaths = paths.map(filePath => normalize(resolve(process.cwd(), filePath)));
   normalizedPaths.forEach(path => {
-    watchFile(path, () => callback());
+    fs.watchFile(path, () => callback());
   });
 };
 
 module.exports = {
   writeFile,
   watchGlob,
+  updateFileSystemConnector,
+  readFile,
 };
diff --git a/packages/pv-stylemark/tasks/lsg/buildLsgExamples.js b/packages/pv-stylemark/tasks/lsg/buildLsgExamples.js
index 49c53f9..6b9c0d3 100644
--- a/packages/pv-stylemark/tasks/lsg/buildLsgExamples.js
+++ b/packages/pv-stylemark/tasks/lsg/buildLsgExamples.js
@@ -1,12 +1,12 @@
 const { resolve } = require("path");
-const { readFile } = require("fs-extra");
+const { readFile: fsReadFile } = require("fs-extra");
 const hbsInstance = require("handlebars").create();
 
-const { writeFile } = require("../../helper/io-helper");
+const { writeFile, readFile } = require("../../helper/io-helper");
 const { resolveApp, getAppConfig, join } = require("../../helper/paths");
 
 const loadTemplate = async hbsInst => {
-  const templateContent = await readFile(resolve(__dirname, "../templates/lsg-example.hbs"), {
+  const templateContent = await fsReadFile(resolve(__dirname, "../templates/lsg-example.hbs"), {
     encoding: "utf-8",
   });
   return hbsInst.compile(templateContent);
diff --git a/packages/pv-stylemark/webpack-plugin/index.js b/packages/pv-stylemark/webpack-plugin/index.js
index b5cdbce..d6c26cc 100644
--- a/packages/pv-stylemark/webpack-plugin/index.js
+++ b/packages/pv-stylemark/webpack-plugin/index.js
@@ -3,6 +3,7 @@ const Assemble = require("@pro-vision/assemble-lite/Assemble");
 const buildStylemark = require("../scripts/buildStylemarkLsg");
 const { getFilesToWatch, fileGlobes } = require("./getFilesToWatch");
 const { resolveApp, getAppConfig, join } = require("../helper/paths");
+const { updateFileSystemConnector } = require("../helper/io-helper");
 
 const { destPath, componentsSrc } = getAppConfig();
 class PvStylemarkPlugin {
@@ -43,6 +44,7 @@ class PvStylemarkPlugin {
       const buildLsg = buildAssemble || copyStylemarkFiles;
 
       if (buildAssemble) {
+        this.assemble.fs = compiler.outputFileSystem;
         await this.assemble.build(
           {
             baseDir: resolveApp(componentsSrc),
@@ -63,6 +65,7 @@ class PvStylemarkPlugin {
       }
 
       if (buildLsg) {
+        updateFileSystemConnector(compiler.outputFileSystem);
         await buildStylemark({
           // unless files were changed but none was a static stylemark file
           shouldCopyStyleguideFiles: copyStylemarkFiles,