changenode_spec.rb

def changenode hash, keys, value
  endkey = keys.pop
  keys.reduce(hash) { |hash, key|
    hash[key].tap {|h| h.is_a?(Hash) or raise("key '#{key}' is not a hash") }
  }[endkey] = value
end

describe "changenode" do

  let(:node) do
    { "foo" =>
      { "bar" => 4,
        "baz" => 5,
        "deeper" => {
          "foobar" => 3
        }
      },
      "test" => 3
    }
  end

  it "should work for simple case" do
    changenode node, %W[test], 5
    node["test"].should == 5
  end

  it "should work for deeper case" do
    changenode node, %W[foo bar], 5
    node["foo"]["bar"].should == 5
  end

  it "should work for a very deep case" do
    changenode node, %W[foo deeper foobar], 5
    node["foo"]["deeper"]["foobar"].should == 5
  end

  it "should fail somehow for missing mode" do
    expect { changenode node, %W[foo doesntexist foobar], 5 }.to raise_error
  end
end