Limit the size of 'actual'/'expected' before generating diff (#4638)

Author: juergba

lib/reporters/base.js

@@ -190,6 +190,13 @@ function stringifyDiffObjs(err) {
  */
 var generateDiff = (exports.generateDiff = function(actual, expected) {
   try {
+    const diffSize = 2048;
+    if (actual.length > diffSize) {
+      actual = actual.substring(0, diffSize) + ' ... Lines skipped';
+    }
+    if (expected.length > diffSize) {
+      expected = expected.substring(0, diffSize) + ' ... Lines skipped';
+    }
     return exports.inlineDiffs
       ? inlineDiff(actual, expected)
       : unifiedDiff(actual, expected);

test/reporters/base.spec.js

@@ -164,6 +164,34 @@ describe('Base reporter', function() {
         '      \n      actual expected\n      \n      a foobar inline diff\n      '
       );
     });
+
+    it("should truncate overly long 'actual' ", function() {
+      var actual = '';
+      var i = 0;
+      while (i++ < 120) {
+        actual += 'a foo unified diff ';
+      }
+      var expected = 'a bar unified diff';
+
+      inlineDiffsStub.value(false);
+      var output = generateDiff(actual, expected);
+
+      expect(output, 'to match', / \.\.\. Lines skipped/);
+    });
+
+    it("should truncate overly long 'expected' ", function() {
+      var actual = 'a foo unified diff';
+      var expected = '';
+      var i = 0;
+      while (i++ < 120) {
+        expected += 'a bar unified diff ';
+      }
+
+      inlineDiffsStub.value(false);
+      var output = generateDiff(actual, expected);
+
+      expect(output, 'to match', / \.\.\. Lines skipped/);
+    });
   });
 
   describe('inline strings diff', function() {