complete coverage

Author: gurgunday

test/parallel/test-buffer-concat.js

@@ -76,6 +76,13 @@ assert.throws(() => {
 const random10 = common.hasCrypto ?
   require('crypto').randomBytes(10) :
   Buffer.alloc(10, 1);
+const derived18 = Buffer.alloc(18);
+for (let i = 0, j = 0; i < 18; i++) {
+  if (i < 10)
+    derived18[i] = random10[i];
+  else
+    derived18[i] = random10[j++];
+}
 const empty = Buffer.alloc(0);
 
 assert.notDeepStrictEqual(random10, empty);
@@ -85,6 +92,7 @@ assert.deepStrictEqual(Buffer.concat([], 100), empty);
 assert.deepStrictEqual(Buffer.concat([random10], 0), empty);
 assert.deepStrictEqual(Buffer.concat([random10], 10), random10);
 assert.deepStrictEqual(Buffer.concat([random10, random10], 10), random10);
+assert.deepStrictEqual(Buffer.concat([random10, random10], 18), derived18);
 assert.deepStrictEqual(Buffer.concat([empty, random10]), random10);
 assert.deepStrictEqual(Buffer.concat([random10, empty, empty]), random10);