Create output directory if it doesn't exist

Author: gabrielweyer

src/dotnet-ad-core/Validation/WritableFileAttribute.cs

@@ -20,6 +20,7 @@ protected override ValidationResult IsValid(object value, ValidationContext cont
 
             try
             {
+                Directory.CreateDirectory(Path.GetDirectoryName(fullPath));
                 File.WriteAllText(fullPath, "q");
                 return ValidationResult.Success;
             }

tests/dotnet-wad-to-csv-tests/Validation/WritableFileAttributeTests.cs

@@ -50,11 +50,15 @@ public void GivenNonWritableFilePath_WhenGetValidationResult_ThenErrorMessage()
         }
 
         [Fact]
-        public void GivenWritableFilePath_WhenGetValidationResult_ThenNoErrorMessage()
+        public void GivenWritableFilePathInNewDirectory_WhenGetValidationResult_ThenNoErrorMessage()
         {
             // Arrange
 
-            var writableFilePath = Path.GetTempFileName();
+            var writableFilePath = Path.Combine(
+                Path.GetTempPath(),
+                "wad-to-csv-tests",
+                Guid.NewGuid().ToString(),
+                Path.GetRandomFileName());
 
             SetTarget(writableFilePath);