diff --git a/packages/material-ui-lab/src/TreeItem/TreeItem.test.js b/packages/material-ui-lab/src/TreeItem/TreeItem.test.js
index afbd340354de90..7cd21eaa0e4fd7 100644
--- a/packages/material-ui-lab/src/TreeItem/TreeItem.test.js
+++ b/packages/material-ui-lab/src/TreeItem/TreeItem.test.js
@@ -8,10 +8,15 @@ import TreeItem from './TreeItem';
 import TreeView from '../TreeView';
 
 describe('<TreeItem />', () => {
-  // StrictModeViolation: uses Collapse
+  let classes;
+  let mount;
   const render = createClientRender({ strict: false });
-  const mount = createMount({ strict: false });
-  const classes = getClasses(<TreeItem nodeId="one" label="one" />);
+
+  before(() => {
+    // StrictModeViolation: uses Collapse
+    mount = createMount({ strict: false });
+    classes = getClasses(<TreeItem nodeId="one" label="one" />);
+  });
 
   describeConformance(<TreeItem nodeId="one" label="one" />, () => ({
     classes,
diff --git a/packages/material-ui-lab/src/TreeView/TreeView.test.js b/packages/material-ui-lab/src/TreeView/TreeView.test.js
index e298f9c6b74735..a04f140fe6ab17 100644
--- a/packages/material-ui-lab/src/TreeView/TreeView.test.js
+++ b/packages/material-ui-lab/src/TreeView/TreeView.test.js
@@ -8,9 +8,15 @@ import TreeView from './TreeView';
 import TreeItem from '../TreeItem';
 
 describe('<TreeView />', () => {
+  let classes;
+  let mount;
+  // StrictModeViolation: test uses TreeItem
   const render = createClientRender({ strict: false });
-  const mount = createMount({ strict: false });
-  const classes = getClasses(<TreeView />);
+
+  before(() => {
+    mount = createMount({ strict: true });
+    classes = getClasses(<TreeView />);
+  });
 
   describeConformance(<TreeView />, () => ({
     classes,