[rubygems/rubygems] Fix test task name on generated readme when using test-unit

* bundler/lib/bundler/templates/newgem/README.md.tt (Development): Use the
test_task value to get the correct test task name ("test", not "test-unit").
* bundler/spec/commands/newgem_spec.rb (README.md): Add tests for test task
names for each test frameworks.

rubygems/rubygems@2a24708a63

Author: gemmaro

lib/bundler/templates/newgem/README.md.tt

@@ -26,7 +26,7 @@ TODO: Write usage instructions here
 
 ## Development
 
-After checking out the repo, run `bin/setup` to install dependencies.<% if config[:test] %> Then, run `rake <%= config[:test].sub('mini', '').sub('rspec', 'spec') %>` to run the tests.<% end %> You can also run `bin/console` for an interactive prompt that will allow you to experiment.<% if config[:bin] %> Run `bundle exec <%= config[:name] %>` to use the gem in this directory, ignoring other installed copies of this gem.<% end %>
+After checking out the repo, run `bin/setup` to install dependencies.<% if config[:test] %> Then, run `rake <%= config[:test_task] %>` to run the tests.<% end %> You can also run `bin/console` for an interactive prompt that will allow you to experiment.<% if config[:bin] %> Run `bundle exec <%= config[:name] %>` to use the gem in this directory, ignoring other installed copies of this gem.<% end %>
 
 To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and the created tag, and push the `.gem` file to [rubygems.org](https://rubygems.org).
 <% if config[:git] -%>

spec/bundler/commands/newgem_spec.rb

@@ -428,6 +428,22 @@ def bundle_exec_standardrb
         expect(bundled_app("#{gem_name}/README.md").read).not_to include("github.com/bundleuser")
       end
     end
+
+    describe "test task name on readme" do
+      shared_examples_for "test task name on readme" do |framework, task_name|
+        before do
+          bundle "gem #{gem_name} --test=#{framework}"
+        end
+
+        it "renders with correct name" do
+          expect(bundled_app("#{gem_name}/README.md").read).to include("Then, run `rake #{task_name}` to run the tests.")
+        end
+      end
+
+      it_behaves_like "test task name on readme", "test-unit", "test"
+      it_behaves_like "test task name on readme", "minitest", "test"
+      it_behaves_like "test task name on readme", "rspec", "spec"
+    end
   end
 
   it "creates a new git repository" do