Add file path validation

src/Tests/Testing.Common/Testing/AdditionalFile.cs

@@ -21,6 +21,8 @@ public AdditionalFile(string source, string? expectedSource = null, string? path
     {
         Source = source ?? throw new ArgumentNullException(nameof(source));
         ExpectedSource = expectedSource;
+
+        FilePathVerifier.VerifyFilePath(path);
         Path = path;
     }
 

src/Tests/Testing.Common/Testing/FilePathVerifier.cs

@@ -0,0 +1,39 @@
+using System;
+using System.IO;
+using System.Linq;
+
+namespace Roslynator.Testing;
+
+internal static class FilePathVerifier
+{
+    private static readonly char[] _invalidPathChars = Path.GetInvalidPathChars();
+    private static readonly char[] _invalidFileNameChars = Path.GetInvalidFileNameChars();
+
+    public static void VerifyFilePath(string? path)
+    {
+        if (path is null)
+            return;
+
+        if (string.IsNullOrWhiteSpace(path))
+            throw new ArgumentException("File path cannot be empty or contain only whitespace", nameof(path));
+
+        if (path.IndexOfAny(_invalidPathChars) >= 0)
+            throw new ArgumentException("File path contains invalid character(s)", nameof(path));
+
+        if (path[path.Length - 1] == Path.DirectorySeparatorChar
+            || path[path.Length - 1] == Path.AltDirectorySeparatorChar)
+        {
+            throw new ArgumentException("File path cannot end with directory separator", nameof(path));
+        }
+
+        var dirSeparatorIndex = FileSystemHelpers.LastIndexOfDirectorySeparator(path);
+        if (dirSeparatorIndex >= 0)
+        {
+            for (int i = dirSeparatorIndex + 1; i < path.Length; i++)
+            {
+                if (_invalidFileNameChars.Contains(path[i]))
+                    throw new ArgumentException("File name contains invalid character(s)", nameof(path));
+            }
+        }
+    }
+}

src/Tests/Testing.Common/Testing/TestFile.cs

@@ -9,6 +9,8 @@ public TestFile(string source, string? expectedSource = null, string? path = nul
     {
         Source = source;
         ExpectedSource = expectedSource;
+
+        FilePathVerifier.VerifyFilePath(path);
         Path = path;
     }