add specs

lib/polist/struct.rb

@@ -2,17 +2,19 @@
 
 module Polist
   module Struct
-    def self.struct(receiver, *attrs)
-      instance_method(:struct).bind(receiver).call(*attrs)
-    end
-
-    def struct(*attrs)
-      attr_accessor(*attrs)
+    module ClassMethods
+      def struct(*attrs)
+        attr_accessor(*attrs)
 
-      define_method(:initialize) do |*args|
-        raise ArgumentError, "struct size differs" if args.length > attrs.length
-        attrs.zip(args).each { |attr, val| public_send(:"#{attr}=", val) }
+        define_method(:initialize) do |*args|
+          raise ArgumentError, "struct size differs" if args.length > attrs.length
+          attrs.zip(args).each { |attr, val| public_send(:"#{attr}=", val) }
+        end
       end
     end
+
+    def self.included(base)
+      base.extend(ClassMethods)
+    end
   end
 end

spec/polist/builder_spec.rb

@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+class User
+  include Polist::Builder
+
+  builds do |role|
+    case role
+    when /admin/
+      Admin
+    end
+  end
+
+  attr_accessor :role
+
+  def initialize(role)
+    self.role = role
+  end
+end
+
+class Admin < User
+  builds do |role|
+    role == "super_admin" ? SuperAdmin : Admin
+  end
+
+  class SuperAdmin < self
+    def super?
+      true
+    end
+  end
+
+  def super?
+    false
+  end
+end
+
+RSpec.describe Polist::Builder do
+  let(:user) { User.build(role) }
+
+  context "user role" do
+    let(:role) { "user" }
+
+    it "builds user" do
+      expect(user.class).to eq(User)
+      expect(user.role).to eq("user")
+    end
+  end
+
+  context "admin role" do
+    let(:role) { "admin" }
+
+    it "builds admin" do
+      expect(user.class).to eq(Admin)
+      expect(user.role).to eq("admin")
+      expect(user.super?).to eq(false)
+    end
+  end
+
+  context "super_admin role" do
+    let(:role) { "super_admin" }
+
+    it "builds super_admin" do
+      expect(user.class).to eq(Admin::SuperAdmin)
+      expect(user.role).to eq("super_admin")
+      expect(user.super?).to eq(true)
+    end
+  end
+end

spec/polist/struct_spec.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+class Point
+  include Polist::Struct
+
+  struct :x, :y
+end
+
+RSpec.describe Polist::Struct do
+  specify "basic usage" do
+    a = Point.new(15, 25)
+    expect(a.x).to eq(15)
+    expect(a.y).to eq(25)
+  end
+
+  context "too many arguments" do
+    it "raises exception" do
+      expect { Point.new(15, 25, 35) }.to raise_error(ArgumentError, "struct size differs")
+    end
+  end
+
+  context "only 1 argument" do
+    it "defaults to nil" do
+      a = Point.new(15)
+      expect(a.x).to eq(15)
+      expect(a.y).to eq(nil)
+    end
+  end
+end