add unit tests for Jekyll::SeoTag

lib/jekyll-seo-tag.rb

@@ -45,7 +45,7 @@ module Jekyll
 
     def payload
       # site_payload is an instance of UnifiedPayloadDrop. See https://git.io/v5ajm
-      @payload ||= context.registers[:site].site_payload.merge({
+      Jekyll::Utils.deep_merge_hashes(context.registers[:site].site_payload, {
         "page"      => context.registers[:page],
         "paginator" => context["paginator"],
         "seo_tag"   => drop,

spec/jekyll_seo_tag_spec.rb

@@ -0,0 +1,50 @@
+RSpec.describe Jekyll::SeoTag do
+  let(:config)    { { "title" => "site title" } }
+  let(:page_meta) { {} }
+  let(:page)      { make_page(page_meta) }
+  let(:site)      { make_site(config) }
+  let(:render_context) { make_context(:page => page, :site => site) }
+  let(:text) { "" }
+  let(:tag_name) { "github_edit_link" }
+  let(:tokenizer) { Liquid::Tokenizer.new("") }
+  let(:parse_context) { Liquid::ParseContext.new }
+  let(:rendered) { subject.render(render_context) }
+  let(:payload) { subject.send(:payload) }
+
+  subject do
+    tag = described_class.parse(tag_name, text, tokenizer, parse_context)
+    tag.instance_variable_set("@context", render_context)
+    tag
+  end
+
+  before do
+    Jekyll.logger.log_level = :error
+  end
+
+  it "returns the template" do
+    expect(described_class.template).to be_a(Liquid::Template)
+  end
+
+  context "payload" do
+    it "contains the drop" do
+      expect(payload["seo_tag"]).to be_a(Jekyll::SeoTag::Drop)
+    end
+
+    it "contains the Jekyll drop" do
+      expect(payload["jekyll"]).to be_a(Jekyll::Drops::JekyllDrop)
+    end
+
+    it "contains the page" do
+      expect(payload["page"]).to be_a(Jekyll::Page)
+    end
+
+    it "contains the site" do
+      expect(payload["site"]).to be_a(Jekyll::Drops::SiteDrop)
+    end
+  end
+
+  it "renders" do
+    expected = "<!-- Begin Jekyll SEO tag v#{described_class::VERSION} -->"
+    expect(rendered).to match(expected)
+  end
+end