ruby--ruby/spec/rubyspec/library/matrix/minus_spec.rb

require File.expand_path('../../../spec_helper', __FILE__)
require File.expand_path('../fixtures/classes', __FILE__)
require 'matrix'

describe "Matrix#-" do
  before :each do
    @a = Matrix[ [1, 2], [3, 4] ]
    @b = Matrix[ [4, 5], [6, 7] ]
  end

  it "returns the result of subtracting the corresponding elements of other from self" do
    (@a - @b).should == Matrix[ [-3,-3], [-3,-3] ]
  end

  it "returns an instance of Matrix" do
    (@a - @b).should be_kind_of(Matrix)
  end

  it "raises a Matrix::ErrDimensionMismatch if the matrices are different sizes" do
    lambda { @a - Matrix[ [1] ] }.should raise_error(Matrix::ErrDimensionMismatch)
  end

  it "raises a ExceptionForMatrix::ErrOperationNotDefined if other is a Numeric Type" do
    lambda { @a - 2            }.should raise_error(Matrix::ErrOperationNotDefined)
    lambda { @a - 1.2          }.should raise_error(Matrix::ErrOperationNotDefined)
    lambda { @a - bignum_value }.should raise_error(Matrix::ErrOperationNotDefined)
  end

  it "raises a TypeError if other is of wrong type" do
    lambda { @a - nil        }.should raise_error(TypeError)
    lambda { @a - "a"        }.should raise_error(TypeError)
    lambda { @a - [ [1, 2] ] }.should raise_error(TypeError)
    lambda { @a - Object.new }.should raise_error(TypeError)
  end

  describe "for a subclass of Matrix" do
    it "returns an instance of that subclass" do
      m = MatrixSub.ins
      (m-m).should be_an_instance_of(MatrixSub)
    end
  end
end