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shared_examples_for 'inverse evaluator' do
context '#inverse' do
subject { object.inverse }
it 'returns the expected inverse evaluator' do
should eql(expected_inverse)
end
end
end
shared_examples_for 'evaluator' do
it 'round trips transitive evaluators via #inverse' do
if object.kind_of?(Morpher::Evaluator::Transformer) && object.transitive?
object.inverse.inverse.should eql(object)
end
end
it 'round trips evaluators via #node' do
Morpher.compile(object.node).should eql(object)
end
end
shared_examples_for 'predicate evaluator' do
include_examples 'evaluator'
let(:negative_example?) { true }
let(:expected_output) { true }
let(:valid_input) { positive_input }
let(:expected_positive_output) { true }
let(:expected_negative_output) { false }
context 'with positive input' do
it 'evaluates to positive output' do
expect(object.call(positive_input)).to be(expected_positive_output)
end
it 'evaluates to inverted positive output' do
expect(object.inverse.call(positive_input)).to be(!expected_positive_output)
end
it 'evaluates to the same output under #evaluation' do
evaluation = object.evaluation(positive_input)
expect(evaluation.success?).to be(true)
expect(evaluation.input).to be(positive_input)
expect(evaluation.output).to be(expected_positive_output)
end
end
context 'with negative input' do
it 'evaluates to false' do
expect(object.call(negative_input)).to be(false)
end
it 'evaluates to true on inverse' do
expect(object.inverse.call(negative_input)).to be(true)
end
it 'evaluates to the same output under #evaluation' do
evaluation = object.evaluation(negative_input)
expect(evaluation.input).to be(negative_input)
expect(evaluation.success?).to be(true)
expect(evaluation.output).to be(false)
end
end
end
shared_examples_for 'transitive evaluator' do
include_examples 'evaluator'
let(:invalid_input_example?) { true }
it 'signals transitivity via #transitive?' do
expect(object.transitive?).to be(true)
end
it 'round trips valid inputs via #evaluation' do
evaluation = object.evaluation(valid_input)
expect(evaluation.success?).to be(true)
evaluation = object.inverse.evaluation(evaluation.output)
expect(evaluation.output).to eql(valid_input)
expect(evaluation.success?).to be(true)
end
it 'round trips valid inputs via #call' do
forward = object.call(valid_input)
expect(object.inverse.call(forward)).to eql(valid_input)
end
end
shared_examples_for 'intransitive evaluator' do
include_examples 'evaluator'
let(:invalid_input_example?) { true }
it 'signals intransitivity via #transitive?' do
expect(object.transitive?).to be(false)
end
end
shared_examples_for 'transforming evaluator on valid input' do
include_examples 'evaluator'
it 'transforms to expected output via #call' do
result = object.call(valid_input)
expect(result).to eql(expected_output)
end
it 'transforms to expected output via #evaluation' do
evaluation = object.evaluation(valid_input)
expect(evaluation.success?).to eql(true)
expect(evaluation.output).to eql(expected_output)
end
specify '#evaluation' do
evaluation = object.evaluation(valid_input)
expect(evaluation.success?).to be(true)
expect(evaluation.evaluator).to eql(object)
expect(evaluation.input).to eql(valid_input)
expect(evaluation.output).to eql(expected_output)
end
specify '#call' do
expect(object.call(valid_input)).to eql(expected_output)
end
end
shared_examples_for 'transforming evaluator on invalid input' do
it 'raises error for #call' do
expect { object.call(invalid_input) }.to raise_error(
Morpher::Evaluator::Transformer::TransformError
)
end
it 'returns error evaluator for #evaluation' do
evaluation = object.evaluation(invalid_input)
expect(evaluation.success?).to eql(false)
expect(evaluation.output).to be(Morpher::Undefined)
end
let(:expected_exception) do
Morpher::Evaluator::Transformer::TransformError.new(object, invalid_input)
end
specify '#call' do
expect { object.call(invalid_input) }.to raise_error(expected_exception)
end
specify '#evaluation' do
evaluation = object.evaluation(invalid_input)
expect(evaluation.success?).to be(false)
expect(evaluation.evaluator).to eql(object)
expect(evaluation.input).to eql(invalid_input)
expect(evaluation.output).to eql(Morpher::Undefined)
end
end
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