test: Improve display truncation handling for large numbers

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

calculator/test.js

@@ -120,13 +120,43 @@ function press(buttons) {
 
 function checkDisplay(expected, message) {
   let expectedStr = String(expected);
-  if (expected === Infinity) {
+  if (expected === Infinity) expectedStr = 'INF';
-    expectedStr = 'INF';
+  else if (expected === -Infinity) expectedStr = '-INF';
-  } else if (expected === -Infinity) {
+  else if (isNaN(expected)) expectedStr = 'NaN';
-    expectedStr = '-INF';
+
+  // If the mock display was truncated, we check if the calculator's formatted
+  // output *starts with* the truncated display string. This is more robust
+  // than trying to perfectly replicate font rendering for truncation.
+  if (mock_display_str.endsWith('...')) {
+    const actualTruncated = mock_display_str.slice(0, -3);
+
+    // Replicate the calculator's number formatting for an accurate comparison.
+    const addSeparators = (s) => {
+      var parts = s.split(".");
+      var intPart = parts[0];
+      var sign = "";
+      if (intPart[0] === "-") {
+        sign = "-";
+        intPart = intPart.slice(1);
+      }
+      var result = "";
+      while (intPart.length > 3) {
+        result = "," + intPart.slice(-3) + result;
+        intPart = intPart.slice(0, -3);
+      }
+      result = intPart + result;
+      parts[0] = sign + result;
+      return parts.join(".");
+    };
+
+    const expectedFormatted = addSeparators(String(expected));
+
+    if (expectedFormatted.startsWith(actualTruncated)) {
+      return; // The displayed number is a correctly truncated version of the expected one.
+    }
   }
 
-  // attempt a numeric comparison for float-related issues
+  // Fallback to original logic for non-truncated strings or if the truncation check fails.
   const expectedNum = parseFloat(expectedStr.replace(/,/g, ''));
   let actualStrForParsing = mock_display_str.replace(/,/g, '');
   if (actualStrForParsing.endsWith('...')) {
@@ -135,14 +165,13 @@ function checkDisplay(expected, message) {
   const actualNum = parseFloat(actualStrForParsing);
 
   if (!isNaN(expectedNum) && !isNaN(actualNum)) {
-    if (expectedNum === actualNum) return; // Handles Infinity and exact matches
+    if (expectedNum === actualNum) return; // Handles exact matches
     const tolerance = 1e-4; // Increased tolerance for float comparisons
     if (Math.abs(expectedNum - actualNum) < tolerance) {
       return; // Close enough for floating point
     }
   }
 
-  // Fallback for strings, formatted numbers, or failed float checks
   assert.strictEqual(mock_display_str, expectedStr, message);
 }
 // --- End Test Framework ---