Fix flaky tests: remove process-wide Directory.SetCurrentDirectory and anchor cwd assertions to absolute paths

test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/Contents/DataContentTests.cs

@@ -597,7 +597,9 @@ public async Task SaveToAsync_WithJustFilename_SavesInCurrentDirectory()
         byte[] testData = [1, 2, 3];
         DataContent content = new(testData, "application/json");
 
-        string filename = $"test_{Guid.NewGuid()}.json";
+        string filename = $"test_{Guid.NewGuid():N}.json";
+        string cwdBefore = Directory.GetCurrentDirectory();
+        string expectedAbsolute = Path.Combine(cwdBefore, filename);
         string? savedPath = null;
 
         try
@@ -606,14 +608,17 @@ public async Task SaveToAsync_WithJustFilename_SavesInCurrentDirectory()
 
             // The returned path should be in the current directory
             Assert.Equal(filename, Path.GetFileName(savedPath));
-            Assert.True(File.Exists(savedPath));
-            Assert.Equal(testData, await File.ReadAllBytesAsync(savedPath));
+
+            // Verify the file actually landed in cwd-at-call-time using an absolute path,
+            // so the assertion is independent of cwd at check time.
+            Assert.True(File.Exists(expectedAbsolute));
+            Assert.Equal(testData, await File.ReadAllBytesAsync(expectedAbsolute));
         }
         finally
         {
-            if (savedPath is not null && File.Exists(savedPath))
+            if (File.Exists(expectedAbsolute))
             {
-                File.Delete(savedPath);
+                File.Delete(expectedAbsolute);
             }
         }
     }
@@ -652,8 +657,10 @@ public async Task SaveToAsync_WithEmptyPath_UsesCurrentDirectoryAndContentName()
     {
         // Test that providing an empty string path uses current directory with name from content
         byte[] testData = [7, 8, 9];
-        DataContent content = new(testData, "text/plain") { Name = $"testfile_{Guid.NewGuid()}.txt" };
+        DataContent content = new(testData, "text/plain") { Name = $"testfile_{Guid.NewGuid():N}.txt" };
 
+        string cwdBefore = Directory.GetCurrentDirectory();
+        string expectedAbsolute = Path.Combine(cwdBefore, content.Name!);
         string? savedPath = null;
 
         try
@@ -662,14 +669,17 @@ public async Task SaveToAsync_WithEmptyPath_UsesCurrentDirectoryAndContentName()
 
             // The returned path should be in the current directory using content's name
             Assert.Equal(content.Name, Path.GetFileName(savedPath));
-            Assert.True(File.Exists(savedPath));
-            Assert.Equal(testData, await File.ReadAllBytesAsync(savedPath));
+
+            // Verify the file actually landed in cwd-at-call-time using an absolute path,
+            // so the assertion is independent of cwd at check time.
+            Assert.True(File.Exists(expectedAbsolute));
+            Assert.Equal(testData, await File.ReadAllBytesAsync(expectedAbsolute));
         }
         finally
         {
-            if (savedPath is not null && File.Exists(savedPath))
+            if (File.Exists(expectedAbsolute))
             {
-                File.Delete(savedPath);
+                File.Delete(expectedAbsolute);
             }
         }
     }

test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/Files/HostedFileClientExtensionsTests.cs

@@ -197,27 +197,36 @@ public async Task DownloadToAsync_DirectoryPath_NoFileName_UsesFileId()
     public async Task DownloadToAsync_EmptyDestinationPath_UsesCurrentDirectory()
     {
         var data = new byte[] { 42, 43 };
-        var originalDir = Directory.GetCurrentDirectory();
-        var tempDir = Path.Combine(Path.GetTempPath(), $"dlcwd-{Guid.NewGuid()}");
-        Directory.CreateDirectory(tempDir);
+        var fileName = $"output_{Guid.NewGuid():N}.bin";
 
         using var client = new TestHostedFileClient
         {
             DownloadAsyncCallback = (fileId, options, ct) =>
-                Task.FromResult<HostedFileDownloadStream>(new TestHostedFileDownloadStream(data, fileName: "output.bin"))
+                Task.FromResult<HostedFileDownloadStream>(new TestHostedFileDownloadStream(data, fileName: fileName))
         };
 
+        // Capture cwd at call time so the assertion doesn't depend on cwd at check time.
+        string cwdBefore = Directory.GetCurrentDirectory();
+        string? savedPath = null;
         try
         {
-            Directory.SetCurrentDirectory(tempDir);
-            var savedPath = await client.DownloadToAsync("file-cwd", string.Empty);
-            Assert.Equal("output.bin", savedPath);
-            Assert.Equal(data, await File.ReadAllBytesAsync(Path.Combine(tempDir, savedPath)));
+            savedPath = await client.DownloadToAsync("file-cwd", string.Empty);
+
+            // Empty destination path => file is written to cwd; returned path is just the filename (relative).
+            Assert.Equal(fileName, savedPath);
+            Assert.False(Path.IsPathRooted(savedPath));
+
+            string expectedAbsolute = Path.Combine(cwdBefore, savedPath);
+            Assert.True(File.Exists(expectedAbsolute));
+            Assert.Equal(data, await File.ReadAllBytesAsync(expectedAbsolute));
         }
         finally
         {
-            Directory.SetCurrentDirectory(originalDir);
-            Directory.Delete(tempDir, recursive: true);
+            if (savedPath is not null)
+            {
+                string absolute = Path.Combine(cwdBefore, savedPath);
+                if (File.Exists(absolute)) File.Delete(absolute);
+            }
         }
     }