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Testing Condition Evaluation Implementation in Shopify/Liquid

This comprehensive test suite validates the Liquid template engine’s condition evaluation functionality, covering basic comparisons, operators, and complex logical operations.

Test Coverage Overview

The test suite provides extensive coverage of Liquid’s conditional evaluation system, including:

Basic comparison operators (==, !=, , , =)
String containment checks
Array containment verification
Complex logical operations (AND/OR)
UTF-8 and binary encoding compatibility

Implementation Analysis

The testing approach utilizes Minitest framework with a systematic verification of condition evaluation logic. Tests are structured around the Condition class implementation, employing helper methods for consistent evaluation assertions.

Key patterns include:

Context-based evaluation testing
Custom operator definition validation
Type coercion verification
Error handling assessment

Technical Details

Testing infrastructure includes:

Minitest as the testing framework
Custom assertion helpers for evaluation verification
Liquid::Context for environment simulation
Setup methods for test initialization
Error capture and validation mechanisms

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Comprehensive edge case coverage
Isolated test cases with clear purpose
Consistent error handling validation
Proper test setup and teardown
Deprecation warning verification

shopify/liquid

test/unit/condition_unit_test.rb

            
# frozen_string_literal: true

require 'test_helper'

class ConditionUnitTest < Minitest::Test
  include Liquid

  def setup
    @context = Liquid::Context.new
  end

  def test_basic_condition
    assert_equal(false, Condition.new(1, '==', 2).evaluate(Context.new))
    assert_equal(true,  Condition.new(1, '==', 1).evaluate(Context.new))
  end

  def test_default_operators_evalute_true
    assert_evaluates_true(1, '==', 1)
    assert_evaluates_true(1, '!=', 2)
    assert_evaluates_true(1, '<>', 2)
    assert_evaluates_true(1, '<', 2)
    assert_evaluates_true(2, '>', 1)
    assert_evaluates_true(1, '>=', 1)
    assert_evaluates_true(2, '>=', 1)
    assert_evaluates_true(1, '<=', 2)
    assert_evaluates_true(1, '<=', 1)
    # negative numbers
    assert_evaluates_true(1, '>', -1)
    assert_evaluates_true(-1, '<', 1)
    assert_evaluates_true(1.0, '>', -1.0)
    assert_evaluates_true(-1.0, '<', 1.0)
  end

  def test_default_operators_evalute_false
    assert_evaluates_false(1, '==', 2)
    assert_evaluates_false(1, '!=', 1)
    assert_evaluates_false(1, '<>', 1)
    assert_evaluates_false(1, '<', 0)
    assert_evaluates_false(2, '>', 4)
    assert_evaluates_false(1, '>=', 3)
    assert_evaluates_false(2, '>=', 4)
    assert_evaluates_false(1, '<=', 0)
    assert_evaluates_false(1, '<=', 0)
  end

  def test_contains_works_on_strings
    assert_evaluates_true('bob', 'contains', 'o')
    assert_evaluates_true('bob', 'contains', 'b')
    assert_evaluates_true('bob', 'contains', 'bo')
    assert_evaluates_true('bob', 'contains', 'ob')
    assert_evaluates_true('bob', 'contains', 'bob')

    assert_evaluates_false('bob', 'contains', 'bob2')
    assert_evaluates_false('bob', 'contains', 'a')
    assert_evaluates_false('bob', 'contains', '---')
  end

  def test_contains_binary_encoding_compatibility_with_utf8
    assert_evaluates_true('🙈'.b, 'contains', '🙈')
    assert_evaluates_true('🙈', 'contains', '🙈'.b)
  end

  def test_invalid_comparation_operator
    assert_evaluates_argument_error(1, '~~', 0)
  end

  def test_comparation_of_int_and_str
    assert_evaluates_argument_error('1', '>', 0)
    assert_evaluates_argument_error('1', '<', 0)
    assert_evaluates_argument_error('1', '>=', 0)
    assert_evaluates_argument_error('1', '<=', 0)
  end

  def test_hash_compare_backwards_compatibility
    assert_nil(Condition.new({}, '>', 2).evaluate(Context.new))
    assert_nil(Condition.new(2, '>', {}).evaluate(Context.new))
    assert_equal(false, Condition.new({}, '==', 2).evaluate(Context.new))
    assert_equal(true, Condition.new({ 'a' => 1 }, '==', 'a' => 1).evaluate(Context.new))
    assert_equal(true, Condition.new({ 'a' => 2 }, 'contains', 'a').evaluate(Context.new))
  end

  def test_contains_works_on_arrays
    @context          = Liquid::Context.new
    @context['array'] = [1, 2, 3, 4, 5]
    array_expr        = VariableLookup.new("array")

    assert_evaluates_false(array_expr, 'contains', 0)
    assert_evaluates_true(array_expr, 'contains', 1)
    assert_evaluates_true(array_expr, 'contains', 2)
    assert_evaluates_true(array_expr, 'contains', 3)
    assert_evaluates_true(array_expr, 'contains', 4)
    assert_evaluates_true(array_expr, 'contains', 5)
    assert_evaluates_false(array_expr, 'contains', 6)
    assert_evaluates_false(array_expr, 'contains', "1")
  end

  def test_contains_returns_false_for_nil_operands
    @context = Liquid::Context.new
    assert_evaluates_false(VariableLookup.new('not_assigned'), 'contains', '0')
    assert_evaluates_false(0, 'contains', VariableLookup.new('not_assigned'))
  end

  def test_contains_return_false_on_wrong_data_type
    assert_evaluates_false(1, 'contains', 0)
  end

  def test_contains_with_string_left_operand_coerces_right_operand_to_string
    assert_evaluates_true(' 1 ', 'contains', 1)
    assert_evaluates_false(' 1 ', 'contains', 2)
  end

  def test_or_condition
    condition = Condition.new(1, '==', 2)
    assert_equal(false, condition.evaluate(Context.new))

    condition.or(Condition.new(2, '==', 1))

    assert_equal(false, condition.evaluate(Context.new))

    condition.or(Condition.new(1, '==', 1))

    assert_equal(true, condition.evaluate(Context.new))
  end

  def test_and_condition
    condition = Condition.new(1, '==', 1)

    assert_equal(true, condition.evaluate(Context.new))

    condition.and(Condition.new(2, '==', 2))

    assert_equal(true, condition.evaluate(Context.new))

    condition.and(Condition.new(2, '==', 1))

    assert_equal(false, condition.evaluate(Context.new))
  end

  def test_should_allow_custom_proc_operator
    Condition.operators['starts_with'] = proc { |_cond, left, right| left =~ /^#{right}/ }

    assert_evaluates_true('bob', 'starts_with', 'b')
    assert_evaluates_false('bob', 'starts_with', 'o')
  ensure
    Condition.operators.delete('starts_with')
  end

  def test_left_or_right_may_contain_operators
    @context        = Liquid::Context.new
    @context['one'] = @context['another'] = "gnomeslab-and-or-liquid"

    assert_evaluates_true(VariableLookup.new("one"), '==', VariableLookup.new("another"))
  end

  def test_default_context_is_deprecated
    if Gem::Version.new(Liquid::VERSION) >= Gem::Version.new('6.0.0')
      flunk("Condition#evaluate without a context argument is to be removed")
    end

    _out, err = capture_io do
      assert_equal(true, Condition.new(1, '==', 1).evaluate)
    end

    expected = "DEPRECATION WARNING: Condition#evaluate without a context argument is deprecated" \
      " and will be removed from Liquid 6.0.0."
    assert_includes(err.lines.map(&:strip), expected)
  end

  private

  def assert_evaluates_true(left, op, right)
    assert(
      Condition.new(left, op, right).evaluate(@context),
      "Evaluated false: #{left.inspect} #{op} #{right.inspect}",
    )
  end

  def assert_evaluates_false(left, op, right)
    assert(
      !Condition.new(left, op, right).evaluate(@context),
      "Evaluated true: #{left.inspect} #{op} #{right.inspect}",
    )
  end

  def assert_evaluates_argument_error(left, op, right)
    assert_raises(Liquid::ArgumentError) do
      Condition.new(left, op, right).evaluate(@context)
    end
  end
end # ConditionTest