diff --git a/deployment/Dockerfile b/deployment/Dockerfile
index c18c72e0..336d41bc 100644
--- a/deployment/Dockerfile
+++ b/deployment/Dockerfile
@@ -80,10 +80,9 @@ RUN apt-get update -y && \
     fc-cache -fv && apt-get --auto-remove -y remove subversion
 
 ####################
-# Download mathjax (same version as plotly.js extras/)
+# Download mathjax 2.7.5
 
-RUN curl -L https://github.com/plotly/plotly.js/archive/master.tar.gz \
-    | tar -xvzf - --strip-components=3 plotly.js-master/dist/extras/mathjax
+RUN cd / && npm install mathjax@2.7.5 && mv node_modules/mathjax / && rm -rf /node_modules
 
 ####################
 # Install and configure monit
diff --git a/test/dash-preview/mocks/webgl.json b/test/dash-preview/mocks/webgl.json
new file mode 100644
index 00000000..a1a22a9a
--- /dev/null
+++ b/test/dash-preview/mocks/webgl.json
@@ -0,0 +1,8 @@
+{
+  "url": "https://get.webgl.org/",
+  "timeout": "15",
+  "pdf_options": {
+    "pageSize": "Letter",
+    "marginsType": 1
+  }
+}