Add pending specs for jsonld helper (#9750)

* Add specs for JsonLdHelper#first_of_value

* Add specs for JsonLdHelper#supported_context?

spec/helpers/jsonld_helper_spec.rb

@@ -22,11 +22,35 @@ describe JsonLdHelper do
   end
 
   describe '#first_of_value' do
-    pending
+    context 'value.is_a?(Array)' do
+      it 'returns value.first' do
+        value = ['a']
+        expect(helper.first_of_value(value)).to be 'a'
+      end
+    end
+
+    context '!value.is_a?(Array)' do
+      it 'returns value' do
+        value = 'a'
+        expect(helper.first_of_value(value)).to be 'a'
+      end
+    end
   end
 
   describe '#supported_context?' do
-    pending
+    context "!json.nil? && equals_or_includes?(json['@context'], ActivityPub::TagManager::CONTEXT)" do
+      it 'returns true' do
+        json = { '@context' => ActivityPub::TagManager::CONTEXT }.as_json
+        expect(helper.supported_context?(json)).to be true
+      end
+    end
+
+    context 'else' do
+      it 'returns false' do
+        json = nil
+        expect(helper.supported_context?(json)).to be false
+      end
+    end
   end
 
   describe '#fetch_resource' do