assert: fix the string length check for printing the simple diff

Author: puskin

lib/internal/assert/assertion_error.js

@@ -134,7 +134,14 @@ function getStackedDiff(actual, expected) {
 }
 
 function getSimpleDiff(originalActual, actual, originalExpected, expected) {
-  const stringsLen = actual.length + expected.length;
+  let stringsLen = actual.length + expected.length;
+  // Accounting for the quotes wrapping strings
+  if (typeof actual === 'string') {
+    stringsLen -= 2;
+  }
+  if (typeof expected === 'string') {
+    stringsLen -= 2;
+  }
   if (stringsLen <= kMaxShortStringLength && (originalActual !== 0 || originalExpected !== 0)) {
     return { message: `${actual} !== ${expected}`, header: '' };
   }

test/parallel/test-assert-deep.js

@@ -846,6 +846,26 @@ test('Additional tests', () => {
     }
   );
 
+  assert.throws(
+    () => assert.strictEqual('apple', 'pear'),
+    {
+      name: 'AssertionError',
+      message: 'Expected values to be strictly equal:\n\n\'apple\' !== \'pear\'\n'
+    }
+  );
+
+  assert.throws(
+    () => assert.strictEqual('ABABABABABAB', 'BABABABABABA'),
+    {
+      name: 'AssertionError',
+      message: 'Expected values to be strictly equal:\n' +
+        '+ actual - expected\n' +
+        '\n' +
+        "+ 'ABABABABABAB'\n" +
+        "- 'BABABABABABA'\n"
+    }
+  );
+
   assert.notDeepStrictEqual(new Date(), new Date(2000, 3, 14));
 
   assert.throws(