#Based on patch from Wilson Bilkovich

require 'spec_helper'
class SomethingExpected
  attr_accessor :some_value
end

describe "should change(actual, message)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when actual is modified by the block" do
    expect {@instance.some_value = 6}.to change(@instance, :some_value)
  end

  it "should fail when actual is not modified by the block" do
    expect do
      expect {}.to change(@instance, :some_value)
    end.to fail_with("some_value should have changed, but is still 5")
  end
  
  it "provides a #description" do
    change(@instance, :some_value).description.should == "change #some_value"
  end
end

describe "should_not change(actual, message)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when actual is not modified by the block" do
    expect { }.to_not change(@instance, :some_value)
  end

  it "should fail when actual is not modified by the block" do
    expect do
      expect {@instance.some_value = 6}.to_not change(@instance, :some_value)
    end.to fail_with("some_value should not have changed, but did change from 5 to 6")
  end
end

describe "should change { block }" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when actual is modified by the block" do
    expect {@instance.some_value = 6}.to change { @instance.some_value }
  end

  it "should fail when actual is not modified by the block" do
    expect do
      expect {}.to change{ @instance.some_value }
    end.to fail_with("result should have changed, but is still 5")
  end
  
  it "should warn if passed a block using do/end instead of {}" do
    expect do
      expect {}.to change do; end
    end.to raise_error(Rspec::Matchers::MatcherError, /block passed to should or should_not/)
  end
  
  it "provides a #description" do
    change { @instance.some_value }.description.should == "change #result"
  end
end

describe "should_not change { block }" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when actual is modified by the block" do
    expect {}.to_not change{ @instance.some_value }
  end

  it "should fail when actual is not modified by the block" do
    expect do
      expect {@instance.some_value = 6}.to_not change { @instance.some_value }
    end.to fail_with("result should not have changed, but did change from 5 to 6")
  end
  
  it "should warn if passed a block using do/end instead of {}" do
    expect do
      expect {}.to_not change do; end
    end.to raise_error(Rspec::Matchers::MatcherError, /block passed to should or should_not/)
  end
end

describe "should change(actual, message).by(expected)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when attribute is changed by expected amount" do
    expect { @instance.some_value += 1 }.to change(@instance, :some_value).by(1)
  end

  it "should fail when the attribute is changed by unexpected amount" do
    expect do
      expect { @instance.some_value += 2 }.to change(@instance, :some_value).by(1)
    end.to fail_with("some_value should have been changed by 1, but was changed by 2")
  end

  it "should fail when the attribute is changed by unexpected amount in the opposite direction" do
    expect do
      expect { @instance.some_value -= 1 }.to change(@instance, :some_value).by(1)
    end.to fail_with("some_value should have been changed by 1, but was changed by -1")
  end
end

describe "should change{ block }.by(expected)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when attribute is changed by expected amount" do
    expect { @instance.some_value += 1 }.to change{@instance.some_value}.by(1)
  end

  it "should fail when the attribute is changed by unexpected amount" do
    expect do
      expect { @instance.some_value += 2 }.to change{@instance.some_value}.by(1)
    end.to fail_with("result should have been changed by 1, but was changed by 2")
  end

  it "should fail when the attribute is changed by unexpected amount in the opposite direction" do
    expect do
      expect { @instance.some_value -= 1 }.to change{@instance.some_value}.by(1)
    end.to fail_with("result should have been changed by 1, but was changed by -1")
  end
end

describe "should change(actual, message).by_at_least(expected)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when attribute is changed by greater than the expected amount" do
    expect { @instance.some_value += 2 }.to change(@instance, :some_value).by_at_least(1)
  end
  
  it "should pass when attribute is changed by the expected amount" do
    expect { @instance.some_value += 2 }.to change(@instance, :some_value).by_at_least(2)
  end  

  it "should fail when the attribute is changed by less than the expected amount" do
    expect do
      expect { @instance.some_value += 1 }.to change(@instance, :some_value).by_at_least(2)
    end.to fail_with("some_value should have been changed by at least 2, but was changed by 1")
  end

end

describe "should change{ block }.by_at_least(expected)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when attribute is changed by greater than expected amount" do
    expect { @instance.some_value += 2 }.to change{@instance.some_value}.by_at_least(1)
  end
  
  it "should pass when attribute is changed by the expected amount" do
    expect { @instance.some_value += 2 }.to change{@instance.some_value}.by_at_least(2)
  end  

  it "should fail when the attribute is changed by less than the unexpected amount" do
    expect do
      expect { @instance.some_value += 1 }.to change{@instance.some_value}.by_at_least(2)
    end.to fail_with("result should have been changed by at least 2, but was changed by 1")
  end
end


describe "should change(actual, message).by_at_most(expected)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when attribute is changed by less than the expected amount" do
    expect { @instance.some_value += 2 }.to change(@instance, :some_value).by_at_most(3)
  end
  
  it "should pass when attribute is changed by the expected amount" do
    expect { @instance.some_value += 2 }.to change(@instance, :some_value).by_at_most(2)
  end  

  it "should fail when the attribute is changed by greater than the expected amount" do
    expect do
      expect { @instance.some_value += 2 }.to change(@instance, :some_value).by_at_most(1)
    end.to fail_with("some_value should have been changed by at most 1, but was changed by 2")
  end

end

describe "should change{ block }.by_at_most(expected)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 5
  end

  it "should pass when attribute is changed by less than expected amount" do
    expect { @instance.some_value += 2 }.to change{@instance.some_value}.by_at_most(3)
  end
  
  it "should pass when attribute is changed by the expected amount" do
    expect { @instance.some_value += 2 }.to change{@instance.some_value}.by_at_most(2)
  end  

  it "should fail when the attribute is changed by greater than the unexpected amount" do
    expect do
      expect { @instance.some_value += 2 }.to change{@instance.some_value}.by_at_most(1)
    end.to fail_with("result should have been changed by at most 1, but was changed by 2")
  end
end

describe "should change(actual, message).from(old)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 'string'
  end

  it "should pass when attribute is == to expected value before executing block" do
    expect { @instance.some_value = "astring" }.to change(@instance, :some_value).from("string")
  end

  it "should fail when attribute is not == to expected value before executing block" do
    expect do
      expect { @instance.some_value = "knot" }.to change(@instance, :some_value).from("cat")
    end.to fail_with("some_value should have initially been \"cat\", but was \"string\"")
  end
end

describe "should change{ block }.from(old)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 'string'
  end

  it "should pass when attribute is == to expected value before executing block" do
    expect { @instance.some_value = "astring" }.to change{@instance.some_value}.from("string")
  end

  it "should fail when attribute is not == to expected value before executing block" do
    expect do
      expect { @instance.some_value = "knot" }.to change{@instance.some_value}.from("cat")
    end.to fail_with("result should have initially been \"cat\", but was \"string\"")
  end
end

describe "should change(actual, message).to(new)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 'string'
  end
  
  it "should pass when attribute is == to expected value after executing block" do
    expect { @instance.some_value = "cat" }.to change(@instance, :some_value).to("cat")
  end

  it "should fail when attribute is not == to expected value after executing block" do
    expect do
      expect { @instance.some_value = "cat" }.to change(@instance, :some_value).from("string").to("dog")
    end.to fail_with("some_value should have been changed to \"dog\", but is now \"cat\"")
  end
end

describe "should change{ block }.to(new)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 'string'
  end
  
  it "should pass when attribute is == to expected value after executing block" do
    expect { @instance.some_value = "cat" }.to change{@instance.some_value}.to("cat")
  end

  it "should fail when attribute is not == to expected value after executing block" do
    expect do
      expect { @instance.some_value = "cat" }.to change{@instance.some_value}.from("string").to("dog")
    end.to fail_with("result should have been changed to \"dog\", but is now \"cat\"")
  end
end

describe "should change(actual, message).from(old).to(new)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 'string'
  end
  
  it "should pass when #to comes before #from" do
    expect { @instance.some_value = "cat" }.to change(@instance, :some_value).to("cat").from("string")
  end

  it "should pass when #from comes before #to" do
    expect { @instance.some_value = "cat" }.to change(@instance, :some_value).from("string").to("cat")
  end
  
  it "should show the correct messaging when #after and #to are different" do
    expect do
      expect { @instance.some_value = "cat" }.to change(@instance, :some_value).from("string").to("dog")
    end.to fail_with("some_value should have been changed to \"dog\", but is now \"cat\"")
  end
  
  it "should show the correct messaging when #before and #from are different" do
    expect do
      expect { @instance.some_value = "cat" }.to change(@instance, :some_value).from("not_string").to("cat")
    end.to fail_with("some_value should have initially been \"not_string\", but was \"string\"")
  end
end

describe "should change{ block }.from(old).to(new)" do
  before(:each) do
    @instance = SomethingExpected.new
    @instance.some_value = 'string'
  end
  
  it "should pass when #to comes before #from" do
    expect { @instance.some_value = "cat" }.to change{@instance.some_value}.to("cat").from("string")
  end

  it "should pass when #from comes before #to" do
    expect { @instance.some_value = "cat" }.to change{@instance.some_value}.from("string").to("cat")
  end
end

describe Rspec::Matchers::Change do
  it "should work when the receiver has implemented #send" do
    @instance = SomethingExpected.new
    @instance.some_value = "string"
    def @instance.send(*args); raise "DOH! Library developers shouldn't use #send!" end
    
    expect {
      expect { @instance.some_value = "cat" }.to change(@instance, :some_value)
    }.to_not raise_error
  end
end