Add external config feature spec

spec/features/external_config_spec.rb

@@ -0,0 +1,79 @@
+RSpec.describe "External application config", with_gem: :some_gem do
+  before do
+    gem.main_file.write(main_file)
+  end
+
+  let(:external_config) { Kangaru.application.config.external.serialise }
+
+  shared_examples :does_not_set_external_config do
+    it "does not raise any errors" do
+      expect { gem.load! }.not_to raise_error
+    end
+
+    it "does not set any external config" do
+      gem.load!
+      expect(external_config).to be_empty
+    end
+  end
+
+  shared_examples :sets_external_config do
+    it "does not raise any errors" do
+      expect { gem.load! }.not_to raise_error
+    end
+
+    it "sets the external config" do
+      gem.load!
+      expect(external_config).to eq(frodo: { race: "hobbit", age: 48 })
+    end
+  end
+
+  context "when config_path is not set" do
+    let(:main_file) do
+      <<~RUBY
+        require "kangaru"
+
+        module SomeGem
+          extend Kangaru::Initialiser
+        end
+      RUBY
+    end
+
+    include_examples :does_not_set_external_config
+  end
+
+  context "when config_path is set" do
+    let(:main_file) do
+      <<~RUBY
+        require "kangaru"
+
+        module SomeGem
+          extend Kangaru::Initialiser
+
+          Kangaru.application.configure do |config|
+            config.application.config_path = "#{config_path}"
+          end
+        end
+      RUBY
+    end
+
+    let(:config_path) { gem.dir.join("config.yml") }
+
+    context "and no config exists at the specified path" do
+      include_examples :does_not_set_external_config
+    end
+
+    context "and config exists at the specified path" do
+      let(:config_file) do
+        <<~YAML
+          frodo:
+            race: hobbit
+            age: 48
+        YAML
+      end
+
+      before { config_path.write(config_file) }
+
+      include_examples :sets_external_config
+    end
+  end
+end