diff --git a/test/dummyNotebook_helper.js b/test/dummyNotebook_helper.js
index <HASH>..<HASH> 100644
--- a/test/dummyNotebook_helper.js
+++ b/test/dummyNotebook_helper.js
@@ -1,24 +1,8 @@
-import Immutable from 'immutable';
+import { fromJS } from 'commutable';
 
 // This is only here as a stop gap until we test innards directly.
 
 require.extensions['.ipynb'] = require.extensions['.json'];
 const notebook = require('../test-notebooks/multiples.ipynb');
 
-// Convert the multiline strings from a raw notebook so we have a nice
-// consistent structure for Immutable.JS
-for(const cell of notebook.cells) {
-  if(cell.outputs) {
-    for(const output of cell.outputs) {
-      if (output.data) {
-        for (const mimetype in output.data) {
-          if (Array.isArray(output.data[mimetype])) {
-            output.data[mimetype] = output.data[mimetype].join('');
-          }
-        }
-      }
-    }
-  }
-}
-
-export default Immutable.fromJS(notebook);
+export default fromJS(notebook);
Update test to use commutable.