Assert the logger works in Capistrano

Follow up on the previous commits to remove the logger instance from the
Config class, which was set by Capistrano.

It didn't actually log anything before, as it wrote to a `StringIO.new`.
Log now to the configured logger based on the application's config.

I see no harm in making the logger work. By default it will log to the
`appsignal.log` file. If apps have configured it to log to stdout, they
have deliberately configured that so there should be no problem.

spec/lib/appsignal/capistrano2_spec.rb

@@ -7,6 +7,8 @@
     let(:out_stream) { std_stream }
     let(:output) { out_stream.read }
     let(:config) { build_config }
+    let(:log_stream) { StringIO.new }
+    let(:logs) { log_contents(log_stream) }
     let(:capistrano_config) do
       Capistrano::Configuration.new.tap do |c|
         c.set(:rails_env, "production")
@@ -17,7 +19,10 @@
         c.dry_run = false
       end
     end
-    before { Appsignal::Integrations::Capistrano.tasks(capistrano_config) }
+    before do
+      Appsignal.internal_logger = test_logger(log_stream)
+      Appsignal::Integrations::Capistrano.tasks(capistrano_config)
+    end
 
     def run
       capture_stdout(out_stream) do
@@ -125,6 +130,7 @@ def run
               run
               expect(output).to include \
                 "Not notifying of deploy, config is not active for environment: production"
+              expect(logs).to contains_log(:error, "Push API key not set after loading config")
             end
           end
         end

spec/lib/appsignal/capistrano3_spec.rb

@@ -10,12 +10,12 @@
     let(:config) { build_config(:env => env, :options => options) }
     let(:out_stream) { std_stream }
     let(:output) { out_stream.read }
-    let(:logger) { Logger.new(out_stream) }
+    let(:log_stream) { StringIO.new }
+    let(:logs) { log_contents(log_stream) }
     let!(:capistrano_config) do
       Capistrano::Configuration.reset!
       Capistrano::Configuration.env.tap do |c|
         c.set(:log_level, :error)
-        c.set(:logger, logger)
         c.set(:rails_env, "production")
         c.set(:repository, "main")
         c.set(:deploy_to, "/home/username/app")
@@ -29,7 +29,10 @@
         :user => "batman"
       }
     end
-    before { Rake::Task["appsignal:deploy"].reenable }
+    before do
+      Appsignal.internal_logger = test_logger(log_stream)
+      Rake::Task["appsignal:deploy"].reenable
+    end
 
     def run
       capture_std_streams(out_stream, out_stream) do
@@ -141,6 +144,7 @@ def run
               run
               expect(output).to include \
                 "Not notifying of deploy, config is not active for environment: production"
+              expect(logs).to contains_log(:error, "Push API key not set after loading config")
             end
           end
         end