Refs #11418. Added testhelper for temporary files

Code/Mantid/Framework/PythonInterface/test/testhelpers/CMakeLists.txt

@@ -5,6 +5,7 @@
 set ( PY_FILES
   __init__.py
   algorithm_decorator.py
+  tempfile_wrapper.py
 )
 
 # Copy python files to output directory

Code/Mantid/Framework/PythonInterface/test/testhelpers/tempfile_wrapper.py

@@ -0,0 +1,46 @@
+from tempfile import NamedTemporaryFile
+import os
+
+
+class TemporaryFileHelper(object):
+    """Helper class for temporary files in unit tests
+
+    This class is a small helper for using temporary files for unit test. On instantiation, a temporary file will be
+    created (using NamedTemporaryFile from the tempfile module). If the string argument to the constructor is not empty,
+    its content will be written to that file. The getName()-method provides the name of the temporary file, which can
+    for example be passed to an algorithm that expects a FileProperty. On destruction of the TemporaryFileHelper object,
+    the temporary file is removed automatically using os.unlink().
+
+    Usage:
+      emptyFileHelper = TemporaryFileHelper()
+      fh = open(emptyFileHelper.getName(), 'r+')
+      fh.write("Something or other\n")
+      fh.close()
+
+      filledFileHelper = TemporaryFileHelper("Something or other\n")
+      other = open(filledFileHelper.getName(), 'r')
+      for line in other:
+        print line
+      other.close()
+
+      del emptyFileHelper
+      del filledFileHelper
+    """
+    tempFile = None
+
+    def __init__(self, fileContent=""):
+        self.tempFile = NamedTemporaryFile('r+', delete=False)
+
+        if fileContent:
+            self._setFileContent(fileContent)
+
+    def __del__(self):
+        os.unlink(self.tempFile.name)
+
+    def getName(self):
+        return self.tempFile.name
+
+    def _setFileContent(self, content):
+        fileHandle = open(self.getName(), 'r+')
+        fileHandle.write(content)
+        fileHandle.close()