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Testing Conditional Statement Evaluation in Liquid Template Engine

This integration test suite validates the conditional statement handling in Liquid templating engine. It thoroughly tests comparison operators, equality checks, and nil value handling across different data types and scenarios.

Test Coverage Overview

The test suite provides comprehensive coverage of Liquid’s statement evaluation capabilities:

Boolean comparisons using ==, !=, >, =, <= operators
String equality and inequality checks
Variable comparison with literals and strings
Null/nil value handling
Collection emptiness validation

Implementation Analysis

The testing approach uses Minitest framework with systematic validation of statement outcomes:

Template-based testing using assert_template_result
Variable context injection for dynamic testing
Edge case handling with null values and empty collections
Consistent test structure following arrange-act-assert pattern

Technical Details

Testing infrastructure includes:

Minitest as the testing framework
Liquid module integration
Custom assertion helpers
Ruby’s frozen_string_literal pragma
Template rendering validation utilities

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases with clear purpose
Comprehensive operator coverage
Consistent naming conventions
Edge case consideration
Readable test descriptions

shopify/liquid

test/integration/tags/statements_test.rb

            
# frozen_string_literal: true

require 'test_helper'

class StatementsTest < Minitest::Test
  include Liquid

  def test_true_eql_true
    text = ' {% if true == true %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text)
  end

  def test_true_not_eql_true
    text = ' {% if true != true %} true {% else %} false {% endif %} '
    assert_template_result('  false  ', text)
  end

  def test_true_lq_true
    text = ' {% if 0 > 0 %} true {% else %} false {% endif %} '
    assert_template_result('  false  ', text)
  end

  def test_one_lq_zero
    text = ' {% if 1 > 0 %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text)
  end

  def test_zero_lq_one
    text = ' {% if 0 < 1 %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text)
  end

  def test_zero_lq_or_equal_one
    text = ' {% if 0 <= 0 %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text)
  end

  def test_zero_lq_or_equal_one_involving_nil
    text = ' {% if null <= 0 %} true {% else %} false {% endif %} '
    assert_template_result('  false  ', text)

    text = ' {% if 0 <= null %} true {% else %} false {% endif %} '
    assert_template_result('  false  ', text)
  end

  def test_zero_lqq_or_equal_one
    text = ' {% if 0 >= 0 %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text)
  end

  def test_strings
    text = " {% if 'test' == 'test' %} true {% else %} false {% endif %} "
    assert_template_result('  true  ', text)
  end

  def test_strings_not_equal
    text = " {% if 'test' != 'test' %} true {% else %} false {% endif %} "
    assert_template_result('  false  ', text)
  end

  def test_var_strings_equal
    text = ' {% if var == "hello there!" %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text, { 'var' => 'hello there!' })
  end

  def test_var_strings_are_not_equal
    text = ' {% if "hello there!" == var %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text, { 'var' => 'hello there!' })
  end

  def test_var_and_long_string_are_equal
    text = " {% if var == 'hello there!' %} true {% else %} false {% endif %} "
    assert_template_result('  true  ', text, { 'var' => 'hello there!' })
  end

  def test_var_and_long_string_are_equal_backwards
    text = " {% if 'hello there!' == var %} true {% else %} false {% endif %} "
    assert_template_result('  true  ', text, { 'var' => 'hello there!' })
  end

  # def test_is_nil
  #  text = %| {% if var != nil %} true {% else %} false {% end %} |
  #  @template.assigns = { 'var' => 'hello there!'}
  #  expected = %|  true  |
  #  assert_equal expected, @template.parse(text)
  # end

  def test_is_collection_empty
    text = ' {% if array == empty %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text, { 'array' => [] })
  end

  def test_is_not_collection_empty
    text = ' {% if array == empty %} true {% else %} false {% endif %} '
    assert_template_result('  false  ', text, { 'array' => [1, 2, 3] })
  end

  def test_nil
    text = ' {% if var == nil %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text, { 'var' => nil })

    text = ' {% if var == null %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text, { 'var' => nil })
  end

  def test_not_nil
    text = ' {% if var != nil %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text, { 'var' => 1 })

    text = ' {% if var != null %} true {% else %} false {% endif %} '
    assert_template_result('  true  ', text, { 'var' => 1 })
  end
end # StatementsTest