DuckTesting

Simple data type testing tool

Usage

YARD

```rb require “duck_testing”

DuckTesting::YARD.apply ```

This code automatically generates duck_testing module for all classes in {lib,app}/**/*.rb and prepends them into corresponding classes. In most cases, you might put the code in spec/spec_helper.rb or test/test_helper.rb.

You can include and exclude custom paths by using paths and excluded arguments. For instance, excluding Rails’ controllers and views is written as follows:

rb DuckTesting::YARD.apply(excluded: [%r{^app/(controllers|views)}])

Manually

Suppose there are a class and corresponding duck_testing module:

```rb require “duck_testing”

class Foo # @param [Fixnum, Float] # @return [Fixnum, Float] def double(x) x * 2 end end

module FooDuckTesting def double(x) tester = DuckTesting::Tester.new(self, “double”) tester.test_param(x, [ DuckTesting::Type::ClassInstance.new(Fixnum), DuckTesting::Type::ClassInstance.new(Float) ]) tester.test_return(super, [ DuckTesting::Type::ClassInstance.new(Fixnum), DuckTesting::Type::ClassInstance.new(Float) ]) end end ```

Now you can activate type testing by prepending duck_testing module into the class:

```rb before = Foo.new

before.double(“2”) # => “22”

Foo.send(:prepend, FooDuckTesting)

after = Foo.new

after.double(2) # => 4

after.double(2.0) # => 4.0

after.double(“2”) # ContractViolationError: Contract violation for argument Foo#double ```