test: add unit tests for helper methods in Helper class

Author: manu4543

test/imagekit/helpers/helper_test.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require_relative "../test_helper"
+
+class HelperTest < Minitest::Test
+  def setup
+    @client = Imagekit::Client.new(
+      private_key: "test_private_key",
+      password: "test_password"
+    )
+    @helper = Imagekit::Helpers::Helper.new(client: @client)
+  end
+
+  def test_build_url
+    result = @helper.build_url([])
+    assert_instance_of(String, result)
+    assert_equal("https://ik.imagekit.io/your_imagekit_id/sample-image.jpg?tr=w-400,h-300", result)
+  end
+
+  def test_build_transformation_string
+    result = @helper.build_transformation_string([])
+    assert_instance_of(String, result)
+    assert_equal("w-400,h-300", result)
+  end
+
+  def test_get_authentication_parameters
+    result = @helper.get_authentication_parameters("test_token", 1800)
+    assert_instance_of(Hash, result)
+    assert_equal("test_token", result[:token])
+    assert_equal(1800, result[:expire])
+    assert_equal("dummy_signature", result[:signature])
+  end
+end