cleanup inside finally block; add test to verify throw after max retries

Author: surayya-MS

src/Tests/Microsoft.NET.Build.Containers.UnitTests/RegistryTests.cs

@@ -558,16 +558,56 @@ public async Task DownloadBlobAsync_RetriesOnFailure()
 
         Registry registry = new(repoName, logger, mockRegistryAPI.Object, null, () => TimeSpan.Zero);
 
-        // Act
-        var result = await registry.DownloadBlobAsync(repoName, descriptor, cancellationToken);
+        string? result = null;
+        try
+        {
+            // Act
+            result = await registry.DownloadBlobAsync(repoName, descriptor, cancellationToken);
+
+            // Assert
+            Assert.NotNull(result);
+            Assert.True(File.Exists(result)); // Ensure the file was successfully downloaded
+            mockRegistryAPI.Verify(api => api.Blob.GetStreamAsync(repoName, descriptor.Digest, cancellationToken), Times.Exactly(3)); // Verify retries
+        }
+        finally
+        {
+            // Cleanup
+            if (result != null)
+            {
+                File.Delete(result);
+            }
+        }
+    }
+
+    [Fact]
+    public async Task DownloadBlobAsync_ThrowsAfterMaxRetries()
+    {
+        // Arrange
+        var logger = _loggerFactory.CreateLogger(nameof(DownloadBlobAsync_ThrowsAfterMaxRetries));
 
-        // Assert
-        Assert.NotNull(result);
-        Assert.True(File.Exists(result)); // Ensure the file was successfully downloaded
-        mockRegistryAPI.Verify(api => api.Blob.GetStreamAsync(repoName, descriptor.Digest, cancellationToken), Times.Exactly(3)); // Verify retries
+        var repoName = "testRepo";
+        var descriptor = new Descriptor(SchemaTypes.OciLayerGzipV1, "sha256:testdigest1234", 1234);
+        var cancellationToken = CancellationToken.None;
+
+        var mockRegistryAPI = new Mock<IRegistryAPI>(MockBehavior.Strict);
+        // Simulate 5 failures (assuming your retry logic attempts 5 times before throwing)
+        mockRegistryAPI
+            .SetupSequence(api => api.Blob.GetStreamAsync(repoName, descriptor.Digest, cancellationToken))
+            .ThrowsAsync(new Exception("Simulated failure 1"))
+            .ThrowsAsync(new Exception("Simulated failure 2"))
+            .ThrowsAsync(new Exception("Simulated failure 3"))
+            .ThrowsAsync(new Exception("Simulated failure 4"))
+            .ThrowsAsync(new Exception("Simulated failure 5"));
+
+        Registry registry = new(repoName, logger, mockRegistryAPI.Object, null, () => TimeSpan.Zero);
+
+        // Act & Assert
+        await Assert.ThrowsAsync<UnableToDownloadFromRepositoryException>(async () =>
+        {
+            await registry.DownloadBlobAsync(repoName, descriptor, cancellationToken);
+        });
 
-        //Cleanup
-        File.Delete(result);
+        mockRegistryAPI.Verify(api => api.Blob.GetStreamAsync(repoName, descriptor.Digest, cancellationToken), Times.Exactly(5));
     }
 
     private static NextChunkUploadInformation ChunkUploadSuccessful(Uri requestUri, Uri uploadUrl, int? contentLength, HttpStatusCode code = HttpStatusCode.Accepted)