Define a constant if not defined:

    define_if_not_defined(:A, 1)

    assert_equal 1, A

Define a constant and redefine it:

    define_if_not_defined(:B, 1)
    redefine_without_warning(:B, 2)

    assert_equal 2, B

Redefine a constant which should set the constant:

    redefine_without_warning(:C, 3)

    assert_equal 3, C

Define a constant within a module:

    Math.define_if_not_defined(:FOO, 2 * Math::PI)

    assert_equal 2 * Math::PI, Math::FOO

Define and redefine a constant within a module:

    Math.define_if_not_defined(:BAR, 3)
    Math.redefine_without_warning(:BAR, 5)

    assert_equal 5, Math::BAR

Redefine a constant within a module which should set the constant:

    Math.redefine_without_warning(:AMAZING, 3)

    assert_equal 3, Math::AMAZING