add the test code from crystal

test/README.markdown

@@ -0,0 +1,38 @@
+Parsing
+-------
+
+Some sanity is emerging in the testing of parsers 
+    (Parsers are fiddly in respect to space and order, small changes may and do have unexpected effects)
+
+Parsing is a two step process with parslet:
+  - parse takes an input and outputs hashes/arrays with basic types
+  - tramsform takes the output of parse and generates an ast (as specified by the transformation)
+
+A test tests both phases seperately and again together.
+Each test must thus specify (as instance variables):
+- the string input
+- the parse output
+- the transform output
+
+Magic
+-----
+
+Test are grouped by functionality into cases (classes) and define methods test_*
+Test cases must include ParserHelper, which includes the magic to write the 3 test methods for each 
+test method. See test_basic for easy example.
+
+Example:
+
+  def test_number
+    @string_input    = '42 '
+    @test_output = {:integer => '42'}
+    @transform_output = Parser::IntegerExpression.new(42)
+    @parser = @parser.integer
+  end
+
+The first three lines define the data as described above.
+The last line tells the parser what to parse. This is off couse only needed when a non-root rule is tested
+and should be left out if possible.
+
+As can be seen, there are no asserts. All asserting is done by the created methods, which call 
+the check_* methods in helper.