Mocking in Java using Mocha

Posted by James Mead Sun, 17 Feb 2008 18:10:01 GMT

Ola Bini one of the JRuby guys has released the JtestR tool which allows you to write tests for Java code in Ruby! Ola has bundled a number of Ruby libraries – Mocha, RSpec, Dust, Test::Unit & ActiveSupport – together with JRuby to allow you to write Ruby test cases that test Java code.

He has a couple of examples in the Mock documentation of how to use Mocha...

The first one demonstrates using Mocha to mock an interface (Map).

  import java.util.Map
  import java.util.Iterator
  import java.util.Set
  import java.util.HashMap

  functional_tests do 
    test "that a new HashMap can be created based on another map" do 
      map = Map.new

      map.expects(:size).returns(0)

      iter = Iterator.new
      iter.expects(:hasNext).returns(false)

      set = Set.new
      set.expects(:iterator).returns(iter)

      map.expects(:entrySet).returns(set)

      assert_equals 0, HashMap.new(map).size
    end
  end

The second example demonstrates using Mocha to setup expectations on a real (non-mock) instance (HashMap)...

  import java.util.Iterator
  import java.util.Set
  import java.util.HashMap

  functional_tests do 
    test "that a new HashMap can be created based on another map" do 
      map = mock(HashMap)

      map.expects(:size).returns(0)

      iter = Iterator.new
      iter.expects(:hasNext).returns(false)

      set = Set.new
      set.expects(:iterator).returns(iter)

      map.expects(:entrySet).returns(set)

      assert_equals 0, HashMap.new(map).size
    end
  end

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