require "spec_helper"

describe Array do
  shared_examples_for "a serie calculation" do
    context "when called on a empty array" do
      let(:values) { [] }
      it { lambda { subject }.should raise_exception ZeroDivisionError, "not enough elements" }
    end

    context "when called on a array with only one element" do
      let(:values) { [1] }
      it { lambda { subject }.should raise_exception ZeroDivisionError, "not enough elements" }
    end
  end

  %w(stdev standard_deviation).each do |method|
    describe "##{method}" do
      subject { values.send method }

      it_should_behave_like "a serie calculation"

      context "with integer values" do
        let(:values) { [1, 2, 6, 3, -4, 23] }
        it { should be_close_to 9.32559202767667 }
      end

      context "with float values" do
        let(:values) { [1.0, 2.0, 6.0, 3.0, -4.0, 23.0] }
        it { should be_close_to 9.32559202767667 }
      end

      context "with bigdecimal values" do
        let(:values) { [BigDecimal("1.0"), BigDecimal("2.0"), BigDecimal("6.0"), BigDecimal("3.0"), BigDecimal("-4.0"), BigDecimal("23.0")] }
        it { should be_close_to 9.32559202767667 }
      end
    end
  end

  describe "#stdevp" do
    subject { values.stdevp }

    it_should_behave_like "a serie calculation"

    context "with integer values" do
      let(:values) { [1, 2, 6, 3, -4, 23] }
      it { should be_close_to 8.513061859414755 }
    end

    context "with float values" do
      let(:values) { [1.0, 2.0, 6.0, 3.0, -4.0, 23.0] }
      it { should be_close_to 8.513061859414755 }
    end

    context "with bigdecimal values" do
      let(:values) { [BigDecimal("1.0"), BigDecimal("2.0"), BigDecimal("6.0"), BigDecimal("3.0"), BigDecimal("-4.0"), BigDecimal("23.0")] }
      it { should be_close_to 8.513061859414755 }
    end
  end

  %w(variance sample_variance).each do |method|
    describe "##{method}" do
      subject { values.send method }

      it_should_behave_like "a serie calculation"

      context "with integer values" do
        let(:values) { [1, 2, 6, 3, -4, 23] }
        it { should be_close_to 86.96666666666665 }
      end

      context "with float values" do
        let(:values) { [1.0, 2.0, 6.0, 3.0, -4.0, 23.0] }
        it { should be_close_to 86.96666666666665 }
      end

      context "with bigdecimal values" do
        let(:values) { [BigDecimal("1.0"), BigDecimal("2.0"), BigDecimal("6.0"), BigDecimal("3.0"), BigDecimal("-4.0"), BigDecimal("23.0")] }
        it { should be_close_to 86.96666666666665 }
      end
    end
  end

  describe "#population_variance" do
    subject { values.population_variance }

    it_should_behave_like "a serie calculation"

    context "with integer values" do
      let(:values) { [1, 2, 6, 3, -4, 23] }
      it { should be_close_to 72.47222222222221 }
    end

    context "with float values" do
      let(:values) { [1.0, 2.0, 6.0, 3.0, -4.0, 23.0] }
      it { should be_close_to 72.47222222222221 }
    end

    context "with bigdecimal values" do
      let(:values) { [BigDecimal("1.0"), BigDecimal("2.0"), BigDecimal("6.0"), BigDecimal("3.0"), BigDecimal("-4.0"), BigDecimal("23.0")] }
      it { should be_close_to 72.47222222222221 }
    end
  end
end