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