Added tests for MachOStructure dsl

Added tests for all field types and options.

Also, fixed bug related to calculating
MachoStructure#min_args.

lib/macho/structure.rb

@@ -52,6 +52,11 @@ module Fields
       # To add a new class append it here and add the init method to the def_class_reader method
       # @api private
       CLASS_LIST = %i[lcstr tool_entries two_level_hints_table].freeze
+
+      # A list of fields that don't require arguments
+      # Used to calculate MachOStructure#min_args
+      # @api private
+      NO_ARGS_LIST = %i[two_level_hints_table].freeze
     end
 
     # map of field names to indices
@@ -142,7 +147,7 @@ def field(name, type, **options)
         idx = if @field_idxs.key?(name)
           @field_idxs[name]
         else
-          @min_args += 1 unless options.key?(:default)
+          @min_args += 1 unless options.key?(:default) || Fields::NO_ARGS_LIST.include?(type)
           @field_idxs[name] = @field_idxs.size
           @size_list << nil
           @fmt_list << nil

test/test_structure_dsl.rb

@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+require_relative "helpers"
+
+class MachOStructureTest < Minitest::Test
+  # Test that every field type can be created and that
+  # that information is reflected in the bytesize, min_args
+  # and format.
+  class AllFields < MachO::MachOStructure
+    field :binary, :binary, :size => 16
+    field :string, :string, :size => 32
+    field :int32, :int32
+    field :uint32, :uint32
+    field :uint64, :uint64
+    field :view, :view
+    field :lcstr, :lcstr
+    field :two_level_hints_table, :two_level_hints_table
+    field :tool_entries, :tool_entries
+  end
+
+  def test_all_field_types
+    assert_includes AllFields.instance_methods, :binary
+    assert_includes AllFields.instance_methods, :string
+    assert_includes AllFields.instance_methods, :int32
+    assert_includes AllFields.instance_methods, :uint32
+    assert_includes AllFields.instance_methods, :uint64
+    assert_includes AllFields.instance_methods, :view
+    assert_includes AllFields.instance_methods, :lcstr
+    assert_includes AllFields.instance_methods, :two_level_hints_table
+    assert_includes AllFields.instance_methods, :tool_entries
+
+    assert_equal AllFields.bytesize, 72
+    assert_equal AllFields.format, "a16Z32l=L=Q=L=L="
+    assert_equal AllFields.min_args, 8
+  end
+
+  # Test that fields already defined in the base class
+  # are updated correctly when redefined in the
+  # derived class.
+  class BaseCmd < MachO::MachOStructure
+    field :field1, :uint32
+    field :field2, :uint32
+  end
+
+  class DerivedCmd < BaseCmd
+    field :field1, :uint64
+    field :field2, :uint64
+  end
+
+  def test_updating_fields
+    assert_equal BaseCmd.bytesize, 8
+    assert_equal BaseCmd.format, "L=L="
+    assert_equal DerivedCmd.bytesize, 16
+    assert_equal DerivedCmd.format, "Q=Q="
+  end
+
+  # Tests that make sure that all of the options work
+  # correctly (except for :size which is already tested above).
+  class MaskCmd < MachO::MachOStructure
+    field :mask_field, :uint32, :mask => 0xffff0000
+  end
+
+  def test_mask_option
+    mask_struct = MaskCmd.new(0xffffffff)
+    assert_equal mask_struct.mask_field, 0x0000ffff
+  end
+
+  class UnpackCmd < MachO::MachOStructure
+    field :unpack_field, :binary, :size => 8, :unpack => "L>2"
+  end
+
+  def test_unpack_option
+    numbers = [42, 1337].freeze
+    format_code = "L>2"
+    packed_numbers = numbers.pack(format_code)
+
+    unpack_struct = UnpackCmd.new(packed_numbers)
+    assert_equal unpack_struct.unpack_field, numbers
+  end
+
+  class DefaultCmd < MachO::MachOStructure
+    field :default_field, :uint64, :default => 0
+  end
+
+  def test_default_option
+    default_struct = DefaultCmd.new
+    assert_equal default_struct.default_field, 0
+    default_struct = DefaultCmd.new(4)
+    assert_equal default_struct.default_field, 4
+  end
+
+  class StringCmd < MachO::MachOStructure
+    field :uint32, :uint32, :to_s => true
+  end
+
+  def test_to_s_option
+    string_cmd = StringCmd.new(10)
+    assert_equal string_cmd.to_s, "10"
+  end
+
+  class EndianCmd < MachO::MachOStructure
+    field :uint32_big, :uint32, :endian => :big
+    field :uint32_little, :uint32, :endian => :little
+  end
+
+  def test_endian_option
+    assert_equal EndianCmd.format, "L>L<"
+  end
+end