@@ -1,15 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
-using System.IO;
 using System.Linq;
-using System.Net;
-using System.Net.Http;
-using System.Security.Cryptography.X509Certificates;
-using System.Text;
 using System.Text.RegularExpressions;
-using System.Threading;
-using System.Threading.Tasks;
 using Semmle.Util;
 using Semmle.Util.Logging;
 
@@ -22,9 +15,9 @@ internal sealed partial class FeedManager : IDisposable
         private readonly ILogger logger;
         private readonly IDotNet dotnet;
         private readonly IFileProvider fileProvider;
-        private readonly IDependabotProxy? dependabotProxy;
         private readonly DependencyDirectory emptyPackageDirectory;
         private readonly ImmutableHashSet<string> privateRegistryFeeds;
+        private readonly IFeedManagerIO feedManagerIo;
 
         /// <summary>
         /// Gets whether there are private package registries configured for C#.
@@ -79,12 +72,12 @@ internal sealed partial class FeedManager : IDisposable
         /// </summary>
         public ImmutableHashSet<string> ReachableFallbackFeeds => lazyReachableFallbackFeeds.Value;
 
-        public FeedManager(ILogger logger, IDotNet dotnet, IDependabotProxy? dependabotProxy, IFileProvider fileProvider)
+        public FeedManager(ILogger logger, IDotNet dotnet, IDependabotProxy? dependabotProxy, IFileProvider fileProvider, IFeedManagerIO feedManagerIo)
         {
             this.logger = logger;
             this.dotnet = dotnet;
-            this.dependabotProxy = dependabotProxy;
             this.fileProvider = fileProvider;
+            this.feedManagerIo = feedManagerIo;
             privateRegistryFeeds = dependabotProxy?.RegistryURLs.ToImmutableHashSet() ?? [];
             HasPrivateRegistryFeeds = privateRegistryFeeds.Count > 0;
             emptyPackageDirectory = new DependencyDirectory("empty", "empty package", logger);
@@ -105,17 +98,9 @@ public FeedManager(ILogger logger, IDotNet dotnet, IDependabotProxy? dependabotP
             });
         }
 
-        private string? GetDirectoryName(string path)
+        public FeedManager(ILogger logger, IDotNet dotnet, IDependabotProxy? dependabotProxy, IFileProvider fileProvider)
+            : this(logger, dotnet, dependabotProxy, fileProvider, new FeedManagerIO(logger, dependabotProxy))
         {
-            try
-            {
-                return new FileInfo(path).Directory?.FullName;
-            }
-            catch (Exception exc)
-            {
-                logger.LogWarning($"Failed to get directory of '{path}': {exc}");
-            }
-            return null;
         }
 
         private IEnumerable<string> GetFeeds(Func<IList<string>> getNugetFeeds)
@@ -193,7 +178,7 @@ private IEnumerable<string> FeedsToUseAux(HashSet<string> feedsToConsider)
         public IEnumerable<string> FeedsToUse(string path)
         {
             // Find the path specific feeds.
-            var folder = GetDirectoryName(path);
+            var folder = feedManagerIo.GetDirectoryName(path);
             var feedsToConsider = folder is not null ? GetFeedsFromFolder(folder).ToHashSet() : new HashSet<string>();
 
             return FeedsToUseAux(feedsToConsider);
@@ -238,76 +223,6 @@ public List<string> MakeRestoreFeeds(string path)
             return (timeoutMilliSeconds, tryCount);
         }
 
-        private static async Task<HttpResponseMessage> ExecuteGetRequest(string address, HttpClient httpClient, CancellationToken cancellationToken)
-        {
-            return await httpClient.GetAsync(address, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
-        }
-
-        private bool IsFeedReachable(string feed, int timeoutMilliSeconds, int tryCount)
-        {
-            logger.LogInfo($"Checking if NuGet feed '{feed}' is reachable...");
-
-            // Configure the HttpClient to be aware of the Dependabot Proxy, if used.
-            HttpClientHandler httpClientHandler = new();
-            if (dependabotProxy != null)
-            {
-                httpClientHandler.Proxy = new WebProxy(dependabotProxy.Address);
-
-                if (dependabotProxy.Certificate != null)
-                {
-                    httpClientHandler.ServerCertificateCustomValidationCallback = (message, cert, chain, _) =>
-                    {
-                        if (chain is null || cert is null)
-                        {
-                            var msg = cert is null && chain is null
-                                ? "certificate and chain"
-                                : chain is null
-                                    ? "chain"
-                                    : "certificate";
-                            logger.LogWarning($"Dependabot proxy certificate validation failed due to missing {msg}");
-                            return false;
-                        }
-                        chain.ChainPolicy.TrustMode = X509ChainTrustMode.CustomRootTrust;
-                        chain.ChainPolicy.CustomTrustStore.Add(dependabotProxy.Certificate);
-                        return chain.Build(cert);
-                    };
-                }
-            }
-
-            using HttpClient client = new(httpClientHandler);
-
-            for (var i = 0; i < tryCount; i++)
-            {
-                using var cts = new CancellationTokenSource();
-                cts.CancelAfter(timeoutMilliSeconds);
-                try
-                {
-                    logger.LogInfo($"Attempt {i + 1}/{tryCount} to reach NuGet feed '{feed}'.");
-                    using var response = ExecuteGetRequest(feed, client, cts.Token).GetAwaiter().GetResult();
-                    response.EnsureSuccessStatusCode();
-                    logger.LogInfo($"Querying NuGet feed '{feed}' succeeded.");
-                    return true;
-                }
-                catch (Exception exc)
-                {
-                    if (exc is TaskCanceledException tce &&
-                        tce.CancellationToken == cts.Token &&
-                        cts.Token.IsCancellationRequested)
-                    {
-                        logger.LogInfo($"Didn't receive answer from NuGet feed '{feed}' in {timeoutMilliSeconds}ms.");
-                        timeoutMilliSeconds *= 2;
-                        continue;
-                    }
-
-                    logger.LogInfo($"Querying NuGet feed '{feed}' failed. The reason for the failure: {exc.Message}");
-                    return false;
-                }
-            }
-
-            logger.LogWarning($"Didn't receive answer from NuGet feed '{feed}'. Tried it {tryCount} times.");
-            return false;
-        }
-
         /// <summary>
         /// Retrieves a list of excluded NuGet feeds from the corresponding environment variable.
         /// </summary>
@@ -361,7 +276,7 @@ public bool IsDefaultFeedReachable()
             if (CheckNugetFeedResponsiveness)
             {
                 var (initialTimeout, tryCount) = GetFeedRequestSettings(isFallback: false);
-                return IsFeedReachable(PublicNugetOrgFeed, initialTimeout, tryCount);
+                return feedManagerIo.IsFeedReachable(PublicNugetOrgFeed, initialTimeout, tryCount);
             }
 
             return true;
@@ -380,7 +295,7 @@ private List<string> GetReachableNuGetFeeds(HashSet<string> feedsToCheck, bool i
 
             var (initialTimeout, tryCount) = GetFeedRequestSettings(isFallback);
             var reachableFeeds = feedsToCheck
-                .Where(feed => IsFeedReachable(feed, initialTimeout, tryCount))
+                .Where(feed => feedManagerIo.IsFeedReachable(feed, initialTimeout, tryCount))
                 .ToList();
 
             if (reachableFeeds.Count == 0)
@@ -464,7 +379,7 @@ private ImmutableHashSet<string> GetAllFeeds()
             if (nugetConfigs.Count > 0)
             {
                 var nugetConfigFeeds = nugetConfigs
-                    .Select(GetDirectoryName)
+                    .Select(feedManagerIo.GetDirectoryName)
                     .Where(folder => folder != null)
                     .SelectMany(folder => GetFeedsFromFolder(folder!))
                     .ToHashSet();
 
@@ -0,0 +1,109 @@
+
+using System;
+using System.IO;
+using Semmle.Util.Logging;
+using System.Net.Http;
+using System.Net;
+using System.Security.Cryptography.X509Certificates;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Semmle.Extraction.CSharp.DependencyFetching
+{
+    public class FeedManagerIO : IFeedManagerIO
+    {
+        private readonly ILogger logger;
+        private readonly IDependabotProxy? dependabotProxy;
+
+        public FeedManagerIO(ILogger logger, IDependabotProxy? dependabotProxy)
+        {
+            this.logger = logger;
+            this.dependabotProxy = dependabotProxy;
+        }
+
+        public string? GetDirectoryName(string path)
+        {
+            try
+            {
+                return new FileInfo(path).Directory?.FullName;
+            }
+            catch (Exception exc)
+            {
+                logger.LogWarning($"Failed to get directory of '{path}': {exc}");
+            }
+            return null;
+        }
+
+        private static async Task<HttpResponseMessage> ExecuteGetRequest(string address, HttpClient httpClient, CancellationToken cancellationToken)
+        {
+            return await httpClient.GetAsync(address, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
+        }
+
+        public bool IsFeedReachable(string feed, int timeoutMilliSeconds, int tryCount)
+        {
+            logger.LogInfo($"Checking if NuGet feed '{feed}' is reachable...");
+
+            // Configure the HttpClient to be aware of the Dependabot Proxy, if used.
+            HttpClientHandler httpClientHandler = new();
+            if (dependabotProxy != null)
+            {
+                httpClientHandler.Proxy = new WebProxy(dependabotProxy.Address);
+
+                if (dependabotProxy.Certificate != null)
+                {
+                    httpClientHandler.ServerCertificateCustomValidationCallback = (message, cert, chain, _) =>
+                    {
+                        if (chain is null || cert is null)
+                        {
+                            var msg = cert is null && chain is null
+                                ? "certificate and chain"
+                                : chain is null
+                                    ? "chain"
+                                    : "certificate";
+                            logger.LogWarning($"Dependabot proxy certificate validation failed due to missing {msg}");
+                            return false;
+                        }
+                        chain.ChainPolicy.TrustMode = X509ChainTrustMode.CustomRootTrust;
+                        chain.ChainPolicy.CustomTrustStore.Add(dependabotProxy.Certificate);
+                        return chain.Build(cert);
+                    };
+                }
+            }
+
+            using HttpClient client = new(httpClientHandler);
+
+            for (var i = 0; i < tryCount; i++)
+            {
+                using var cts = new CancellationTokenSource();
+                cts.CancelAfter(timeoutMilliSeconds);
+                try
+                {
+                    logger.LogInfo($"Attempt {i + 1}/{tryCount} to reach NuGet feed '{feed}'.");
+                    using var response = ExecuteGetRequest(feed, client, cts.Token).GetAwaiter().GetResult();
+                    response.EnsureSuccessStatusCode();
+                    logger.LogInfo($"Querying NuGet feed '{feed}' succeeded.");
+                    return true;
+                }
+                catch (Exception exc)
+                {
+                    if (exc is TaskCanceledException tce &&
+                        tce.CancellationToken == cts.Token &&
+                        cts.Token.IsCancellationRequested)
+                    {
+                        logger.LogInfo($"Didn't receive answer from NuGet feed '{feed}' in {timeoutMilliSeconds}ms.");
+                        timeoutMilliSeconds *= 2;
+                        continue;
+                    }
+
+                    logger.LogInfo($"Querying NuGet feed '{feed}' failed. The reason for the failure: {exc.Message}");
+                    return false;
+                }
+            }
+
+            logger.LogWarning($"Didn't receive answer from NuGet feed '{feed}'. Tried it {tryCount} times.");
+            return false;
+        }
+
+
+    }
+}
@@ -0,0 +1,16 @@
+
+namespace Semmle.Extraction.CSharp.DependencyFetching
+{
+    public interface IFeedManagerIO
+    {
+        /// <summary>
+        /// Gets the directory name of the specified path.
+        /// </summary>
+        string? GetDirectoryName(string path);
+
+        /// <summary>
+        /// Returns true if the feed is reachable within the specified timeout and try count.
+        /// </summary>
+        bool IsFeedReachable(string feed, int timeoutMilliSeconds, int tryCount);
+    }
+}