[ANN] xmpfilter 0.3.0: automagic Test::Unit assertions and RSpec expectations

Discussion in 'Ruby' started by Mauricio Fernandez, Oct 16, 2006.

  1. xmpfilter can be obtained from http://eigenclass.org/hiki.rb?xmpfilter
    xmpfilter.rb can generate RSpec expectations as of 0.3.0 (thank you,
    rubykitch!).

    Overview
    ========
    xmpfilter.rb is a small tool that can be used to
    * generate Test::Unit assertions and RSpec expectations semi-automatically
    * annotate source code with intermediate results (a bit like irb
    --simple-prompt but only for the lines explicitly marked with # =>)
    Very useful for example code (such as postings to ruby-talk).

    Usage
    =====
    xmpfilter.rb takes its input from stdin and writes to stdout. It can run in
    several modes (annotation, Test::Unit assertion expansion, RSpec expectation
    generation, marker insertion); see
    xmpfilter.rb -h
    README.emacs and README.vim describe how to use xmpfilter.rb from your editor.

    Example: code annotation
    ========================
    Just add "# =>" markers to the lines whose values you want to be shown:

    a, b = "foo", "baz"
    a + b # =>
    a.size # =>

    will be expanded to (in one keypress in a decent editor, see README.emacs and
    README.vim)

    a, b = "foo", "baz"
    a + b # => "foobaz"
    a.size # => 3

    This saves much cut&pasting when you're posting to ruby-talk/ruby-core (I use
    it all the time).

    Example: assertion generation
    =============================

    xmpfilter.rb can generate assertions based on the current behavior of the code
    to be tested (iow. the current behavior is assumed to be correct and is used
    to generate assertions which won't be modified by further runs of
    xmpfilter.rb), making it quite useful for regression testing.

    Imagine you have a ComplexClass you want to test. You might start with

    class TestComplexClass < Test::Unit::TestCase
    def setup; @o = ComplexClass.new("foo", false) end
    end

    and then want to add some tests:

    def test_insertion
    @o.insert "bar"
    @o.insert "baz"
    # ... assertions here
    end

    At this point, you want to add several assertions to verify that the values
    returned by @o.size, @o.last, @o.first, @o.complex_computation and @o.last(2)
    are correct. You can just write the following and feed the file to
    xmpfilter.rb in -u mode (the # => markers can also be inserted by
    xmpfilter.rb, see README.vim for more information:

    def test_insertion
    @o.insert "bar"
    @o.insert "baz"
    @o.size # =>
    @o.last # =>
    @o.first # =>
    @o.complex_computation # =>
    @o.last(2) # =>
    end

    xmpfilter.rb will run the test and remember what happened in each marked line,
    and then rewrite the code so that it looks for instance like

    def test_insertion
    @o.insert "bar"
    @o.insert "baz"
    assert_equal(2, @o.size)
    assert_equal("baz", @o.last)
    assert_equal("bar", @o.first)
    assert_in_delta(3.14159265358979, @o.complex_computation, 0.0001)
    assert_equal(["baz", "bar"], @o.last(2))
    end

    As you can see, it can save some typing.

    You can edit the generated assertions as you want: xmpfilter.rb will not
    modify lines without the "# =>" marker. xmpfilter.rb can be used repeatedly as
    you add more assertions. Imagine you want to verify that @o.last(3) raises an
    ArgumentError. You can simply add one line marked with # => :

    ...
    assert_in_delta(3.14159265358979, @o.complex_computation, 0.0001)
    assert_equal(["baz", "bar"], @o.last(2))
    @o.last(3) # =>
    end

    and have it expanded by xmpfilter.rb:

    ...
    assert_in_delta(3.14159265358979, @o.complex_computation, 0.0001)
    assert_equal(["baz", "bar"], @o.last(2))
    assert_raise(ArgumentError){ @o.last(3) }
    end


    Example: RSpec expectations
    ===========================
    Here's some code before and after filtering it with xmpfilter.rb:

    class X
    Y = Struct.new:)a)
    def foo(b); b ? Y.new(2) : 2 end
    def bar; raise "No good" end
    def baz; nil end
    def fubar(x); x ** 2.0 + 1 end
    def babar; [1,2] end
    A = 1
    A = 1
    end

    context "Testing xmpfilter's expectation expansion" do
    setup do
    @o = X.new
    end

    specify "Should expand should_equal expectations" do
    @o.foo(true) # =>
    @o.foo(true).a # =>
    @o.foo(false) # =>
    end

    specify "Should expand should_raise expectations" do
    @o.bar # =>
    end

    specify "Should expand should_be_nil expectations" do
    @o.baz # =>
    end

    specify "Should expand correct expectations for complex values" do
    @o.babar # =>
    end

    specify "Should expand should_be_close expectations" do
    @o.fubar(10) # =>
    end
    end


    after piping it to xmpfilter.rb -s:

    class X
    Y = Struct.new:)a)
    def foo(b); b ? Y.new(2) : 2 end
    def bar; raise "No good" end
    def baz; nil end
    def fubar(x); x ** 2.0 + 1 end
    def babar; [1,2] end
    A = 1
    A = 1 # !> already initialized constant A
    end

    context "Testing xmpfilter's expectation expansion" do
    setup do
    @o = X.new
    end

    specify "Should expand should_equal expectations" do
    (@o.foo(true)).should_be_a_kind_of X::Y
    (@o.foo(true).inspect).should_equal "#<struct X::Y a=2>"
    (@o.foo(true).a).should_equal 2
    (@o.foo(false)).should_equal 2
    end

    specify "Should expand should_raise expectations" do
    lambda{(@o.bar)}.should_raise RuntimeError
    end

    specify "Should expand should_be_nil expectations" do
    (@o.baz).should_be_nil
    end

    specify "Should expand correct expectations for complex values" do
    (@o.babar).should_equal [1, 2]
    end

    specify "Should expand should_be_close expectations" do
    (@o.fubar(10)).should_be_close(101.0, 0.0001)
    end
    end


    License
    =======
    xmpfilter.rb is licensed under the same terms as Ruby.

    --
    Mauricio Fernandez - http://eigenclass.org - singular Ruby
     
    Mauricio Fernandez, Oct 16, 2006
    #1
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  2. Mauricio Fernandez

    Peña, Botp Guest

    [mailto:] On Behalf Of Mauricio Fernandez
    # Subject: [ANN] xmpfilter 0.3.0: automagic Test::Unit=20
    # assertions and RSpec expectations

    uber cool. are you a god? :)
    thanks for sharing xmpfilter.
    kind regards -botp
     
    Peña, Botp, Oct 16, 2006
    #2
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