Index: trunk/tests/test_input_data.py
===================================================================
diff -u -r45 -r48
--- trunk/tests/test_input_data.py	(.../test_input_data.py)	(revision 45)
+++ trunk/tests/test_input_data.py	(.../test_input_data.py)	(revision 48)
@@ -111,7 +111,30 @@
         # 3. Then
         assert validation_result
 
+    @pytest.mark.integrationtest
+    def test_given_valid_args_then_removes_duplicates(self):
+        # 1. Given
+        input_data = InputData()
+        input_data.input_variables = ['du', 'du', 'mmy']
+        input_data.input_coordinates = [(42, 4.2)]
+        input_data.input_years = [1989, 1990, 1988, 1989]
+        expected_input_variables = ['du', 'mmy']
+        expected_input_years = [1988, 1989, 1990]
+        validation_result = None
 
+        # 2. When
+        try:
+            validation_result = input_data.validate()
+        except Exception as e_info:
+            pytest.fail(
+                'Exception risen {}'.format(str(e_info)) +
+                ' but not expected.')
+
+        # 3. Then
+        assert validation_result
+        assert input_data.input_variables == expected_input_variables
+        assert input_data.input_years == expected_input_years
+
 class Test_ValidateInputYears:
 
     @pytest.mark.unittest
@@ -133,7 +156,48 @@
         assert validation_result is None
         assert expected_message == str(e_info.value)
 
+
     @pytest.mark.unittest
+    def test_when_unordered_input_years_then_orders_it(self):
+        # 1. Given
+        input_data = InputData()
+        input_data.input_years = [1989, 1990, 1980]
+        expected_input_years = [1980, 1989, 1990]
+        validation_result = None
+
+        # 2. When
+        try:
+            validation_result = input_data.validate_input_years()
+        except Exception as e_info:
+            pytest.fail(
+                'Exception risen {}'.format(str(e_info)) +
+                ' but not expected.')
+
+        # 3. Then
+        assert validation_result
+        assert input_data.input_years == expected_input_years
+
+    @pytest.mark.unittest
+    def test_when_input_years_with_repeated_years_then_removes_them(self):
+        # 1. Given
+        input_data = InputData()
+        input_data.input_years = [1990, 1989, 1989]
+        expected_input_years = [1989, 1990]
+        validation_result = None
+
+        # 2. When
+        try:
+            validation_result = input_data.validate_input_years()
+        except Exception as e_info:
+            pytest.fail(
+                'Exception risen {}'.format(str(e_info)) +
+                ' but not expected.')
+
+        # 3. Then
+        assert validation_result
+        assert input_data.input_years == expected_input_years
+
+    @pytest.mark.unittest
     def test_when_valid_input_years_returns_true(self):
         # 1. Given
         input_data = InputData()
@@ -192,7 +256,27 @@
         # 3. Then
         assert validation_result
 
+    @pytest.mark.unittest
+    def test_given_input_variables_then_removes_duplicates(self):
+        # 1. Given
+        input_data = InputData()
+        input_data.input_variables = ['du', 'du', 'mmy']
+        expected_input_variables = ['du', 'mmy']
+        validation_result = None
 
+        # 2. When
+        try:
+            validation_result = input_data.validate_input_variables()
+        except Exception as e_info:
+            pytest.fail(
+                'Exception risen {}'.format(str(e_info)) +
+                ' but not expected.')
+
+        # 3. Then
+        assert validation_result
+        assert input_data.input_variables == expected_input_variables
+
+
 class Test_ValidateInputCoordinates:
 
     @pytest.mark.unittest
Index: trunk/SDToolBox/data_acquisition.py
===================================================================
diff -u -r45 -r48
--- trunk/SDToolBox/data_acquisition.py	(.../data_acquisition.py)	(revision 45)
+++ trunk/SDToolBox/data_acquisition.py	(.../data_acquisition.py)	(revision 48)
@@ -84,7 +84,7 @@
         """
         if not self.input_variables:
             raise IOError(om.error_no_valid_list_of_vars)
-        self.input_variables = set(self.input_variables)
+        self.input_variables = list(set(self.input_variables))
         return True
 
     def validate_input_years(self):