Started tests for Lexer

tests.py

@@ -0,0 +1,48 @@
+import unittest
+
+class Lexer( unittest.TestCase):
+
+    def test_instance(self):
+        from arithmetic import Lexer
+        lexer = Lexer( '5x3 ' )
+        self.assertEqual( lexer.text, '5x3 ' )
+        self.assertEqual( lexer.offset, 0 )
+
+    def test_gettoken_null_text(self):
+        from arithmetic import Lexer
+        lexer = Lexer( '' )
+        lexer.gettoken()
+        self.assertEqual( lexer.value, None )
+        self.assertEqual( lexer.type, '' )
+
+    def test_gettoken_f(self):
+        from arithmetic import Lexer
+        lexer = Lexer( ' 5 ' )
+        lexer.gettoken()
+        self.assertEqual( lexer.value, '5' )
+        self.assertEqual( lexer.type, 'f' )
+
+    def test_gettoken_n(self):
+        from arithmetic import Lexer
+        lexer = Lexer( ' name ' )
+        lexer.gettoken()
+        self.assertEqual( lexer.value, 'name' )
+        self.assertEqual( lexer.type, 'n' )
+
+    def test_gettoken_power(self):
+        from arithmetic import Lexer
+        lexer = Lexer( ' ** ' )
+        lexer.gettoken()
+        self.assertEqual( lexer.value, '**' )
+        self.assertEqual( lexer.type, 'o' )
+
+    def test_gettoken_plus(self):
+        from arithmetic import Lexer
+        lexer = Lexer( ' + ' )
+        lexer.gettoken()
+        self.assertEqual( lexer.value, '+' )
+        self.assertEqual( lexer.type, 'o' )
+
+if __name__ == '__main__':
+    unittest.main()
+