  
This tests the value of stringValue for a single file- and multiple files-<input type="file"> control.


Default value (no files selected):
accessibilityController.accessibleElementById("singleFileUpload").stringValue: AXValue: (None)
accessibilityController.accessibleElementById("multipleFileUpload").stringValue: AXValue: (None)

Drag and drop a single file:
accessibilityController.accessibleElementById("singleFileUpload").stringValue: AXValue: file1.txt
accessibilityController.accessibleElementById("multipleFileUpload").stringValue: AXValue: file1.txt

Drag and drop two files:
accessibilityController.accessibleElementById("singleFileUpload").stringValue: AXValue: (None)
accessibilityController.accessibleElementById("multipleFileUpload").stringValue: AXValue: 2 files