ahem/spec/ast/index_spec.rb

RSpec.describe AST::Index do
  it 'evaluates array index' do
    expect(
      AST::Index.new(
        AST::Array.new(
          [AST::Number.new(1.0), AST::Number.new(2.0), AST::Number.new(3.0)]
        ),
        AST::Number.new(2.0)
      )
        .execute(Environment.new)
    ).to eq(3.0)
  end

  it 'evaluates hash index' do
    expect(
      AST::Index.new(
        AST::Hash.new(
          a: AST::Number.new(1.0),
          b: AST::Number.new(2.0),
          c: AST::Number.new(3.0)
        ),
        AST::Atom.new(:b)
      )
        .execute(Environment.new)
    ).to eq(2.0)
  end

  it 'raises for out of bounds array index' do
    expect {
      AST::Index.new(
        AST::Array.new(
          [AST::Number.new(1.0), AST::Number.new(2.0), AST::Number.new(3.0)]
        ),
        AST::Number.new(3.0)
      )
        .execute(Environment.new)
    }.to raise_error('Array index out of bounds')
  end

  it 'raises for non-integral key on array' do
    expect {
      AST::Index.new(
        AST::Array.new(
          [AST::Number.new(1.0), AST::Number.new(2.0), AST::Number.new(3.0)]
        ),
        AST::Number.new(1.5)
      )
        .execute(Environment.new)
    }.to raise_error('Array index requires integer key')

    expect {
      AST::Index.new(
        AST::Array.new(
          [AST::Number.new(1.0), AST::Number.new(2.0), AST::Number.new(3.0)]
        ),
        AST::String.new('5')
      )
        .execute(Environment.new)
    }.to raise_error('Array index requires integer key')

    expect {
      AST::Index.new(
        AST::Array.new(
          [AST::Number.new(1.0), AST::Number.new(2.0), AST::Number.new(3.0)]
        ),
        AST::Atom.new(:atom)
      )
        .execute(Environment.new)
    }.to raise_error('Array index requires integer key')
  end

  it 'raises for missing hash key' do
    expect {
      AST::Index.new(
        AST::Hash.new(
          {
            a: AST::Number.new(1.0),
            b: AST::Number.new(2.0),
            c: AST::Number.new(3.0)
          }
        ),
        AST::Atom.new(:d)
      )
        .execute(Environment.new)
    }.to raise_error('Key d does not exist on object')
  end
end