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Testing Standard Tag Operations in Liquid Template Engine

This test suite validates core functionality of Liquid’s standard tags through comprehensive integration tests. It ensures proper handling of template rendering, control flow structures, and variable assignments in the Liquid templating system.

Test Coverage Overview

The test suite provides extensive coverage of Liquid’s standard tag functionality.

Key areas tested include:

Template transformation and text rendering
Comment block handling
Variable assignment and capture operations
Case statement logic and conditionals
Cycle tag functionality
Size calculations for arrays and hashes

Edge cases are thoroughly validated including empty strings, null values, and syntax error scenarios.

Implementation Analysis

The testing approach utilizes Minitest framework with systematic verification of template rendering outcomes.

Key patterns include:

assert_template_result method to compare expected vs actual output
Structured test methods for specific tag functionalities
Error condition validation using assert_raises
Complex template parsing scenarios with nested tags

Technical Details

Testing Infrastructure:

Framework: Minitest
Test Helper Integration
Custom assertion methods for template validation
Ruby-based test implementation
Integration with Liquid module

Best Practices Demonstrated

The test suite exemplifies robust testing practices through comprehensive coverage and structured organization.

Notable practices include:

Systematic test case organization
Thorough edge case coverage
Clear test method naming
Consistent assertion patterns
Proper test isolation

shopify/liquid

test/integration/tags/standard_tag_test.rb

            
# frozen_string_literal: true

require 'test_helper'

class StandardTagTest < Minitest::Test
  include Liquid

  def test_no_transform
    assert_template_result(
      'this text should come out of the template without change...',
      'this text should come out of the template without change...',
    )

    assert_template_result('blah', 'blah')
    assert_template_result('<blah>', '<blah>')
    assert_template_result('|,.:', '|,.:')
    assert_template_result('', '')

    text = %(this shouldnt see any transformation either but has multiple lines
              as you can clearly see here ...)
    assert_template_result(text, text)
  end

  def test_has_a_block_which_does_nothing
    assert_template_result(
      %(the comment block should be removed  .. right?),
      %(the comment block should be removed {%comment%} be gone.. {%endcomment%} .. right?),
    )

    assert_template_result('', '{%comment%}{%endcomment%}')
    assert_template_result('', '{%comment%}{% endcomment %}')
    assert_template_result('', '{% comment %}{%endcomment%}')
    assert_template_result('', '{% comment %}{% endcomment %}')
    assert_template_result('', '{%comment%}comment{%endcomment%}')
    assert_template_result('', '{% comment %}comment{% endcomment %}')
    assert_template_result('', '{% comment %} 1 {% comment %} 2 {% endcomment %} 3 {% endcomment %}')

    assert_template_result('', '{%comment%}{%blabla%}{%endcomment%}')
    assert_template_result('', '{% comment %}{% blabla %}{% endcomment %}')
    assert_template_result('', '{%comment%}{% endif %}{%endcomment%}')
    assert_template_result('', '{% comment %}{% endwhatever %}{% endcomment %}')
    assert_template_result('', '{% comment %}{% raw %} {{%%%%}}  }} { {% endcomment %} {% comment {% endraw %} {% endcomment %}')
    assert_template_result('', '{% comment %}{% " %}{% endcomment %}')
    assert_template_result('', '{% comment %}{%%}{% endcomment %}')

    assert_template_result('foobar', 'foo{%comment%}comment{%endcomment%}bar')
    assert_template_result('foobar', 'foo{% comment %}comment{% endcomment %}bar')
    assert_template_result('foobar', 'foo{%comment%} comment {%endcomment%}bar')
    assert_template_result('foobar', 'foo{% comment %} comment {% endcomment %}bar')

    assert_template_result('foo  bar', 'foo {%comment%} {%endcomment%} bar')
    assert_template_result('foo  bar', 'foo {%comment%}comment{%endcomment%} bar')
    assert_template_result('foo  bar', 'foo {%comment%} comment {%endcomment%} bar')

    assert_template_result('foobar', 'foo{%comment%}
                                     {%endcomment%}bar')
  end

  def test_hyphenated_assign
    assigns = { 'a-b' => '1' }
    assert_template_result('a-b:1 a-b:2', 'a-b:{{a-b}} {%assign a-b = 2 %}a-b:{{a-b}}', assigns)
  end

  def test_assign_with_colon_and_spaces
    assigns = { 'var' => { 'a:b c' => { 'paged' => '1' } } }
    assert_template_result('var2: 1', '{%assign var2 = var["a:b c"].paged %}var2: {{var2}}', assigns)
  end

  def test_capture
    assigns = { 'var' => 'content' }
    assert_template_result(
      'content foo content foo ',
      '{{ var2 }}{% capture var2 %}{{ var }} foo {% endcapture %}{{ var2 }}{{ var2 }}',
      assigns,
    )
  end

  def test_capture_detects_bad_syntax
    assert_raises(SyntaxError) do
      assert_template_result(
        'content foo content foo ',
        '{{ var2 }}{% capture %}{{ var }} foo {% endcapture %}{{ var2 }}{{ var2 }}',
        { 'var' => 'content' },
      )
    end
  end

  def test_case
    assigns = { 'condition' => 2 }
    assert_template_result(
      ' its 2 ',
      '{% case condition %}{% when 1 %} its 1 {% when 2 %} its 2 {% endcase %}',
      assigns,
    )

    assigns = { 'condition' => 1 }
    assert_template_result(
      ' its 1 ',
      '{% case condition %}{% when 1 %} its 1 {% when 2 %} its 2 {% endcase %}',
      assigns,
    )

    assigns = { 'condition' => 3 }
    assert_template_result(
      '',
      '{% case condition %}{% when 1 %} its 1 {% when 2 %} its 2 {% endcase %}',
      assigns,
    )

    assigns = { 'condition' => "string here" }
    assert_template_result(
      ' hit ',
      '{% case condition %}{% when "string here" %} hit {% endcase %}',
      assigns,
    )

    assigns = { 'condition' => "bad string here" }
    assert_template_result(
      '',
      '{% case condition %}{% when "string here" %} hit {% endcase %}',\
      assigns,
    )
  end

  def test_case_with_else
    assigns = { 'condition' => 5 }
    assert_template_result(
      ' hit ',
      '{% case condition %}{% when 5 %} hit {% else %} else {% endcase %}',
      assigns,
    )

    assigns = { 'condition' => 6 }
    assert_template_result(
      ' else ',
      '{% case condition %}{% when 5 %} hit {% else %} else {% endcase %}',
      assigns,
    )

    assigns = { 'condition' => 6 }
    assert_template_result(
      ' else ',
      '{% case condition %} {% when 5 %} hit {% else %} else {% endcase %}',
      assigns,
    )
  end

  def test_case_on_size
    assert_template_result('',  '{% case a.size %}{% when 1 %}1{% when 2 %}2{% endcase %}', { 'a' => [] })
    assert_template_result('1', '{% case a.size %}{% when 1 %}1{% when 2 %}2{% endcase %}', { 'a' => [1] })
    assert_template_result('2', '{% case a.size %}{% when 1 %}1{% when 2 %}2{% endcase %}', { 'a' => [1, 1] })
    assert_template_result('',  '{% case a.size %}{% when 1 %}1{% when 2 %}2{% endcase %}', { 'a' => [1, 1, 1] })
    assert_template_result('',  '{% case a.size %}{% when 1 %}1{% when 2 %}2{% endcase %}', { 'a' => [1, 1, 1, 1] })
    assert_template_result('',  '{% case a.size %}{% when 1 %}1{% when 2 %}2{% endcase %}', { 'a' => [1, 1, 1, 1, 1] })
  end

  def test_case_on_size_with_else
    assert_template_result(
      'else',
      '{% case a.size %}{% when 1 %}1{% when 2 %}2{% else %}else{% endcase %}',
      { 'a' => [] },
    )

    assert_template_result(
      '1',
      '{% case a.size %}{% when 1 %}1{% when 2 %}2{% else %}else{% endcase %}',
      { 'a' => [1] },
    )

    assert_template_result(
      '2',
      '{% case a.size %}{% when 1 %}1{% when 2 %}2{% else %}else{% endcase %}',
      { 'a' => [1, 1] },
    )

    assert_template_result(
      'else',
      '{% case a.size %}{% when 1 %}1{% when 2 %}2{% else %}else{% endcase %}',
      { 'a' => [1, 1, 1] },
    )

    assert_template_result(
      'else',
      '{% case a.size %}{% when 1 %}1{% when 2 %}2{% else %}else{% endcase %}',
      { 'a' => [1, 1, 1, 1] },
    )

    assert_template_result(
      'else',
      '{% case a.size %}{% when 1 %}1{% when 2 %}2{% else %}else{% endcase %}',
      { 'a' => [1, 1, 1, 1, 1] },
    )
  end

  def test_case_on_length_with_else
    assert_template_result(
      'else',
      '{% case a.empty? %}{% when true %}true{% when false %}false{% else %}else{% endcase %}',
      {},
    )

    assert_template_result(
      'false',
      '{% case false %}{% when true %}true{% when false %}false{% else %}else{% endcase %}',
      {},
    )

    assert_template_result(
      'true',
      '{% case true %}{% when true %}true{% when false %}false{% else %}else{% endcase %}',
      {},
    )

    assert_template_result(
      'else',
      '{% case NULL %}{% when true %}true{% when false %}false{% else %}else{% endcase %}',
      {},
    )
  end

  def test_assign_from_case
    # Example from the shopify forums
    code = "{% case collection.handle %}{% when 'menswear-jackets' %}{% assign ptitle = 'menswear' %}{% when 'menswear-t-shirts' %}{% assign ptitle = 'menswear' %}{% else %}{% assign ptitle = 'womenswear' %}{% endcase %}{{ ptitle }}"
    assert_template_result("menswear",   code, { "collection" => { 'handle' => 'menswear-jackets' } })
    assert_template_result("menswear",   code, { "collection" => { 'handle' => 'menswear-t-shirts' } })
    assert_template_result("womenswear", code, { "collection" => { 'handle' => 'x' } })
    assert_template_result("womenswear", code, { "collection" => { 'handle' => 'y' } })
    assert_template_result("womenswear", code, { "collection" => { 'handle' => 'z' } })
  end

  def test_case_when_or
    code = '{% case condition %}{% when 1 or 2 or 3 %} its 1 or 2 or 3 {% when 4 %} its 4 {% endcase %}'
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 1 })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 2 })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 3 })
    assert_template_result(' its 4 ', code, { 'condition' => 4 })
    assert_template_result('', code, { 'condition' => 5 })

    code = '{% case condition %}{% when 1 or "string" or null %} its 1 or 2 or 3 {% when 4 %} its 4 {% endcase %}'
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 1 })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 'string' })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => nil })
    assert_template_result('', code, { 'condition' => 'something else' })
  end

  def test_case_when_comma
    code = '{% case condition %}{% when 1, 2, 3 %} its 1 or 2 or 3 {% when 4 %} its 4 {% endcase %}'
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 1 })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 2 })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 3 })
    assert_template_result(' its 4 ', code, { 'condition' => 4 })
    assert_template_result('', code, { 'condition' => 5 })

    code = '{% case condition %}{% when 1, "string", null %} its 1 or 2 or 3 {% when 4 %} its 4 {% endcase %}'
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 1 })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => 'string' })
    assert_template_result(' its 1 or 2 or 3 ', code, { 'condition' => nil })
    assert_template_result('', code, { 'condition' => 'something else' })
  end

  def test_case_when_comma_and_blank_body
    code = '{% case condition %}{% when 1, 2 %} {% assign r = "result" %} {% endcase %}{{ r }}'
    assert_template_result('result', code, { 'condition' => 2 })
  end

  def test_assign
    assert_template_result('variable', '{% assign a = "variable"%}{{a}}')
  end

  def test_assign_unassigned
    assigns = { 'var' => 'content' }
    assert_template_result('var2:  var2:content', 'var2:{{var2}} {%assign var2 = var%} var2:{{var2}}', assigns)
  end

  def test_assign_an_empty_string
    assert_template_result('', '{% assign a = ""%}{{a}}')
  end

  def test_assign_is_global
    assert_template_result('variable', '{%for i in (1..2) %}{% assign a = "variable"%}{% endfor %}{{a}}')
  end

  def test_case_detects_bad_syntax
    assert_raises(SyntaxError) do
      assert_template_result('',  '{% case false %}{% when %}true{% endcase %}', {})
    end

    assert_raises(SyntaxError) do
      assert_template_result('',  '{% case false %}{% huh %}true{% endcase %}', {})
    end
  end

  def test_cycle
    assert_template_result('one', '{%cycle "one", "two"%}')
    assert_template_result('one two', '{%cycle "one", "two"%} {%cycle "one", "two"%}')
    assert_template_result(' two', '{%cycle "", "two"%} {%cycle "", "two"%}')

    assert_template_result('one two one', '{%cycle "one", "two"%} {%cycle "one", "two"%} {%cycle "one", "two"%}')

    assert_template_result(
      'text-align: left text-align: right',
      '{%cycle "text-align: left", "text-align: right" %} {%cycle "text-align: left", "text-align: right"%}',
    )
  end

  def test_multiple_cycles
    assert_template_result(
      '1 2 1 1 2 3 1',
      '{%cycle 1,2%} {%cycle 1,2%} {%cycle 1,2%} {%cycle 1,2,3%} {%cycle 1,2,3%} {%cycle 1,2,3%} {%cycle 1,2,3%}',
    )
  end

  def test_multiple_named_cycles
    assert_template_result(
      'one one two two one one',
      '{%cycle 1: "one", "two" %} {%cycle 2: "one", "two" %} {%cycle 1: "one", "two" %} {%cycle 2: "one", "two" %} {%cycle 1: "one", "two" %} {%cycle 2: "one", "two" %}',
    )
  end

  def test_multiple_named_cycles_with_names_from_context
    assigns = { "var1" => 1, "var2" => 2 }
    assert_template_result(
      'one one two two one one',
      '{%cycle var1: "one", "two" %} {%cycle var2: "one", "two" %} {%cycle var1: "one", "two" %} {%cycle var2: "one", "two" %} {%cycle var1: "one", "two" %} {%cycle var2: "one", "two" %}',
      assigns,
    )
  end

  def test_size_of_array
    assigns = { "array" => [1, 2, 3, 4] }
    assert_template_result('array has 4 elements', "array has {{ array.size }} elements", assigns)
  end

  def test_size_of_hash
    assigns = { "hash" => { a: 1, b: 2, c: 3, d: 4 } }
    assert_template_result('hash has 4 elements', "hash has {{ hash.size }} elements", assigns)
  end

  def test_illegal_symbols
    assert_template_result('', '{% if true == empty %}?{% endif %}', {})
    assert_template_result('', '{% if true == null %}?{% endif %}', {})
    assert_template_result('', '{% if empty == true %}?{% endif %}', {})
    assert_template_result('', '{% if null == true %}?{% endif %}', {})
  end

  def test_ifchanged
    assigns = { 'array' => [1, 1, 2, 2, 3, 3] }
    assert_template_result('123', '{%for item in array%}{%ifchanged%}{{item}}{% endifchanged %}{%endfor%}', assigns)

    assigns = { 'array' => [1, 1, 1, 1] }
    assert_template_result('1', '{%for item in array%}{%ifchanged%}{{item}}{% endifchanged %}{%endfor%}', assigns)
  end

  def test_multiline_tag
    assert_template_result('0 1 2 3', "0{%\nfor i in (1..3)\n%} {{\ni\n}}{%\nendfor\n%}")
  end
end # StandardTagTest