diff --git a/packages/core/index.ts b/packages/core/index.ts
index 822ac111..eb825360 100644
--- a/packages/core/index.ts
+++ b/packages/core/index.ts
@@ -12,6 +12,7 @@ export { default as nodeInputRule } from './src/inputRules/nodeInputRule'
 export { default as markInputRule } from './src/inputRules/markInputRule'
 export { default as markPasteRule } from './src/pasteRules/markPasteRule'
 
+export { default as capitalize } from './src/utils/capitalize'
 export { default as getSchema } from './src/utils/getSchema'
 export { default as generateHtml } from './src/utils/generateHtml'
 export { default as getHtmlFromFragment } from './src/utils/getHtmlFromFragment'
diff --git a/packages/core/src/Editor.ts b/packages/core/src/Editor.ts
index 3e4b448e..b474ac8b 100644
--- a/packages/core/src/Editor.ts
+++ b/packages/core/src/Editor.ts
@@ -10,6 +10,7 @@ import getMarkAttrs from './utils/getMarkAttrs'
 import removeElement from './utils/removeElement'
 import getSchemaTypeByName from './utils/getSchemaTypeByName'
 import getHtmlFromFragment from './utils/getHtmlFromFragment'
+import createStyleTag from './utils/createStyleTag'
 import CommandManager from './CommandManager'
 import ExtensionManager from './ExtensionManager'
 import EventEmitter from './EventEmitter'
@@ -18,6 +19,7 @@ import Node from './Node'
 import Mark from './Mark'
 import defaultPlugins from './plugins'
 import * as coreCommands from './commands'
+import style from './style'
 
 export type Command = (props: {
   editor: Editor,
@@ -118,10 +120,7 @@ export class Editor extends EventEmitter {
     this.extensionManager.resolveConfigs()
     this.createView()
     this.registerCommands(coreCommands)
-
-    if (this.options.injectCSS) {
-      require('./style.css')
-    }
+    this.injectCSS()
 
     this.proxy.focus(this.options.autoFocus)
   }
@@ -143,6 +142,15 @@ export class Editor extends EventEmitter {
     return this.commandManager.createChain()
   }
 
+  /**
+   * Inject CSS styles.
+   */
+  private injectCSS() {
+    if (this.options.injectCSS && document) {
+      this.css = createStyleTag(style)
+    }
+  }
+
   /**
    * Update editor options.
    *
diff --git a/packages/core/src/style.css b/packages/core/src/style.ts
similarity index 94%
rename from packages/core/src/style.css
rename to packages/core/src/style.ts
index b41718f4..ce819062 100644
--- a/packages/core/src/style.css
+++ b/packages/core/src/style.ts
@@ -1,4 +1,4 @@
-.ProseMirror {
+const style = `.ProseMirror {
   position: relative;
 }
 
@@ -49,4 +49,6 @@
 
 .ProseMirror-focused .ProseMirror-gapcursor {
   display: block;
-}
+}`
+
+export default style
diff --git a/packages/core/src/utils/createStyleTag.ts b/packages/core/src/utils/createStyleTag.ts
new file mode 100644
index 00000000..b9078034
--- /dev/null
+++ b/packages/core/src/utils/createStyleTag.ts
@@ -0,0 +1,8 @@
+export default function createStyleTag(style: string): HTMLStyleElement {
+  const styleNode = document.createElement('style')
+
+  styleNode.innerHTML = style
+  document.getElementsByTagName('head')[0].appendChild(styleNode)
+
+  return styleNode
+}
diff --git a/tests/cypress.json b/tests/cypress.json
index 3db2baab..e99c1117 100644
--- a/tests/cypress.json
+++ b/tests/cypress.json
@@ -1,7 +1,7 @@
 {
   "baseUrl": "http://localhost:3000",
-  "integrationFolder": "../docs/src/",
-  "testFiles": "**/*.spec.js",
+  "integrationFolder": "../",
+  "testFiles": "{docs,tests}/**/*.spec.{js,ts}",
   "viewportWidth": 1280,
   "viewportHeight": 1280
 }
diff --git a/tests/cypress/integration/core/capitalize.spec.ts b/tests/cypress/integration/core/capitalize.spec.ts
new file mode 100644
index 00000000..2693a958
--- /dev/null
+++ b/tests/cypress/integration/core/capitalize.spec.ts
@@ -0,0 +1,11 @@
+/// <reference types="cypress" />
+
+import { capitalize } from '@tiptap/core'
+
+describe('capitalize test', () => {
+  it('capitalize a word', () => {
+    const capitalized = capitalize('test')
+
+    expect(capitalized).to.eq('Test')
+  })
+})
diff --git a/tests/cypress/integration/core/example.spec.ts b/tests/cypress/integration/core/example.spec.ts
new file mode 100644
index 00000000..985f70da
--- /dev/null
+++ b/tests/cypress/integration/core/example.spec.ts
@@ -0,0 +1,5 @@
+describe('example test', () => {
+  it('should work', () => {
+    expect('<p>Example Text</p>').to.eq('<p>Example Text</p>')
+  })
+})
diff --git a/tests/cypress/tsconfig.json b/tests/cypress/tsconfig.json
new file mode 100644
index 00000000..974e84cd
--- /dev/null
+++ b/tests/cypress/tsconfig.json
@@ -0,0 +1,13 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "noEmit": false,
+    "sourceMap": false,
+    "types": [
+      "cypress",
+    ],
+  },
+  "include": [
+    "./*/*.ts"
+  ]
+}