ruby--ruby/spec/ruby/library/matrix/diagonal_spec.rb

require_relative '../../spec_helper'

ruby_version_is ""..."3.1" do
  require_relative 'fixtures/classes'
  require 'matrix'

  describe "Matrix.diagonal" do
    before :each do
      @m = Matrix.diagonal(10, 11, 12, 13, 14)
    end

    it "returns an object of type Matrix" do
      @m.should be_kind_of(Matrix)
    end

    it "returns a square Matrix of the right size" do
      @m.column_size.should == 5
      @m.row_size.should == 5
    end

    it "sets the diagonal to the arguments" do
      (0..4).each do |i|
        @m[i, i].should == i + 10
      end
    end

    it "fills all non-diagonal cells with 0" do
      (0..4).each do |i|
        (0..4).each do |j|
          if i != j
            @m[i, j].should == 0
          end
        end
      end
    end

    describe "for a subclass of Matrix" do
      it "returns an instance of that subclass" do
        MatrixSub.diagonal(1).should be_an_instance_of(MatrixSub)
      end
    end
  end

  describe "Matrix.diagonal?" do
    it "returns true for a diagonal Matrix" do
      Matrix.diagonal([1, 2, 3]).diagonal?.should be_true
    end

    it "returns true for a zero square Matrix" do
      Matrix.zero(3).diagonal?.should be_true
    end

    it "returns false for a non diagonal square Matrix" do
      Matrix[[0, 1], [0, 0]].diagonal?.should be_false
      Matrix[[1, 2, 3], [1, 2, 3], [1, 2, 3]].diagonal?.should be_false
    end

    it "returns true for an empty 0x0 matrix" do
      Matrix.empty(0,0).diagonal?.should be_true
    end

    it "raises an error for rectangular matrices" do
      [
        Matrix[[0], [0]],
        Matrix[[0, 0]],
        Matrix.empty(0, 2),
        Matrix.empty(2, 0),
      ].each do |rectangular_matrix|
        -> {
          rectangular_matrix.diagonal?
        }.should raise_error(Matrix::ErrDimensionMismatch)
      end
    end
  end
end