soml-parser/test/README.md

##Running Tests

To run all tests, type

    ruby test/test_all.rb

to run just a single, replace all with what you want to test. Minitest accept a -n option to run just a single test. So while developing i often write things like 

    ruby test/test_class.rb -n test_class_ops_parse
    
Notice tough the _parse at the end, while you will find no such function. The Magic (explained below) renerates three
functions per case. Your options are _parse , _tranform , or if it's really bad, _ast (this should really work when the previous two work)

###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.

### Negative tests

Notice there are no test to test how the parser fails. In other words test of grammar it does not understand, or that isn't even ruby. Such things would be nice off course, but it's early days.