add missing test for scenario when destination file is larger than so…

…urce file (it needs to be truncated) (#64537)
dotnet · Jan 31, 2022 · d201ebb · d201ebb
1 parent ca6716a
commit d201ebb
Showing 1 changed file with 16 additions and 0 deletions.
diff --git a/src/libraries/System.IO.FileSystem/tests/File/Copy.cs b/src/libraries/System.IO.FileSystem/tests/File/Copy.cs
@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.Linq;
+using System.Security.Cryptography;
 using Xunit;
 
 namespace System.IO.Tests
@@ -350,6 +351,21 @@ public void WindowsAlternateDataStreamOverwrite(string defaultStream, string alt
             Assert.Throws<IOException>(() => Copy(testFileAlternateStream, testFile2, overwrite: true));
             Assert.Throws<IOException>(() => Copy(testFileAlternateStream, testFile2 + alternateStream, overwrite: true));
         }
+
+        [Fact]
+        public void DestinationFileIsTruncatedWhenItsLargerThanSourceFile()
+        {
+            string sourcePath = GetTestFilePath();
+            string destPath = GetTestFilePath();
+
+            byte[] content = RandomNumberGenerator.GetBytes(1000);
+            File.WriteAllBytes(sourcePath, content);
+            File.WriteAllBytes(destPath, RandomNumberGenerator.GetBytes(content.Length * 2));
+
+            Copy(sourcePath, destPath, overwrite: true);
+
+            Assert.Equal(content, File.ReadAllBytes(destPath));
+        }
     }
 
     /// <summary>