ci: install only gems required for running tests (#129)

Author: kou

Diff for: .github/workflows/test.yml

@@ -66,8 +66,12 @@ jobs:
         with:
           ruby-version: ${{ matrix.ruby-version }}
       - name: Install as gem
+        env:
+          BUNDLE_PATH__SYSTEM: "true"
+          BUNDLE_WITHOUT: "benchmark:development"
         run: |
           rake install
+          bundle install
       - name: Test
         run: |
           ruby -run -e mkdir -- tmp

Diff for: Gemfile

@@ -6,9 +6,15 @@ git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 gemspec
 
 group :development do
-  gem "benchmark_driver"
   gem "bundler"
   gem "rake"
+end
+
+group :benchmark do
+  gem "benchmark_driver"
+end
+
+group :test do
   gem "test-unit"
   gem "test-unit-ruby-core"
 end