Add some checks to catch test failure

Really just checking that the setup is able to create test files so it
is known they were there then removed.
Windows tests really need verification of
recycle, which is not present.

tests/test_script_main.py

@@ -18,6 +18,8 @@ def file():
         dir=op.expanduser("~"), prefix="send2trash_test", delete=False
     )
     file.close()
+    # Verify file was actually created
+    assert op.exists(file.name) is True
     yield file.name
     # Cleanup trash files on supported platforms
     if sys.platform != "win32":