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