diff --git a/calculator/test.js b/calculator/test.js
index 41323f9..44d49e1 100644
--- a/calculator/test.js
+++ b/calculator/test.js
@@ -119,7 +119,12 @@ function press(buttons) {
 }
 
 function checkDisplay(expected, message) {
-  const expectedStr = String(expected);
+  let expectedStr = String(expected);
+  if (expected === Infinity) {
+    expectedStr = 'INF';
+  } else if (expected === -Infinity) {
+    expectedStr = '-INF';
+  }
 
   // attempt a numeric comparison for float-related issues
   const expectedNum = parseFloat(expectedStr.replace(/,/g, ''));