auth: fix tests for Windows compatibility

- Set USERPROFILE env var on Windows (HOME on Unix)
- Add cross-platform DirectoryIsFile test for write failures

auth/signin_flow_test.go

@@ -3,6 +3,7 @@ package auth
 import (
 	"os"
 	"path/filepath"
+	"runtime"
 	"testing"
 )
 
@@ -267,19 +268,27 @@ func TestConcurrentAccess(t *testing.T) {
 
 // TestFileSystemEdgeCases tests filesystem-related edge cases
 func TestFileSystemEdgeCases(t *testing.T) {
-	tmpDir := setupTestDir(t)
+	t.Run("DirectoryIsFile", func(t *testing.T) {
+		tmpDir := t.TempDir()
 
-	t.Run("ReadOnlyDirectory", func(t *testing.T) {
-		// Make .ollama directory read-only
-		ollamaDir := filepath.Join(tmpDir, ".ollama")
-		os.Chmod(ollamaDir, 0o500)
-		defer os.Chmod(ollamaDir, 0o755) // Restore for cleanup
+		// Create a file where .ollama directory should be
+		ollamaPath := filepath.Join(tmpDir, ".ollama")
+		if err := os.WriteFile(ollamaPath, []byte("not a directory"), 0o600); err != nil {
+			t.Fatalf("failed to create blocking file: %v", err)
+		}
 
-		// Try to write - should fail because can't create temp file
+		// Override home directory
+		if runtime.GOOS == "windows" {
+			t.Setenv("USERPROFILE", tmpDir)
+		} else {
+			t.Setenv("HOME", tmpDir)
+		}
+
+		// Try to write - should fail because .ollama is a file, not a directory
 		state := &SignInState{Name: "newuser", Email: "new@example.com"}
 		err := SetSignInState(state)
 		if err == nil {
-			t.Error("should fail to write in read-only directory")
+			t.Error("should fail when .ollama is a file instead of directory")
 		}
 	})
 }

auth/signin_state_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"runtime"
 	"testing"
 	"time"
 )
@@ -20,8 +21,12 @@ func setupTestDir(t *testing.T) string {
 		t.Fatalf("failed to create .ollama dir: %v", err)
 	}
 
-	// Override home directory for tests
-	t.Setenv("HOME", tmpDir)
+	// Override home directory for tests (platform-specific)
+	if runtime.GOOS == "windows" {
+		t.Setenv("USERPROFILE", tmpDir)
+	} else {
+		t.Setenv("HOME", tmpDir)
+	}
 
 	return tmpDir
 }