enhanced error handling and test cases

* raising RuntimeError if `APPD_CONF_DIR` is provided but directory does not exist
* added version directory `stub-app-dynamics-agent.zip`
* test if config file gets succesfully copied
* test if error is raised when provided directory does not exist

Author: vchrisb

lib/java_buildpack/framework/app_dynamics_agent.rb

@@ -201,10 +201,13 @@ def override_default_config_remote
       def override_default_config_local
         return unless @application.environment['APPD_CONF_DIR']
 
-        app_conf_dir = @application.environment['APPD_CONF_DIR']
+        app_conf_dir = @application.root + @application.environment['APPD_CONF_DIR']
+
+        raise "AppDynamics configuration source dir #{app_conf_dir} does not exist" unless Dir.exist?(app_conf_dir)
+
         @logger.info { "Copy override configuration files from #{app_conf_dir}" }
         CONFIG_FILES.each do |conf_file|
-          conf_file_path = @application.root + app_conf_dir + conf_file
+          conf_file_path = app_conf_dir + conf_file
 
           next unless File.file?(conf_file_path)
 

spec/fixtures/framework_app_dynamics_agent/BOOT-INF/classes/appdynamics/conf/app-agent-config.xml

@@ -1,3 +1,4 @@
+<!-- sourced by APPD_CONF_DIR -->
 <app-agent-configuration>
     <configuration-properties>
         <property name="agent-overwrite" value="false"/>

spec/fixtures/stub-app-dynamics-agent.zip

@@ -199,6 +199,19 @@
            cache_fixture: 'stub-app-dynamics-agent.zip' do
 
           component.compile
+          expect(File.read(sandbox + "ver21.1.0.31582/conf/app-agent-config.xml")).to include "sourced by APPD_CONF_DIR"
+        end
+      end
+    
+      context do
+
+        let(:environment) { { 'APPD_CONF_DIR' => 'BOOT-INF/classes/appdynamics/conf-false' } }
+
+        it 'sets APPD_CONF_DIR env var to copy config files from incorrect app dir',
+           app_fixture: 'framework_app_dynamics_agent',
+           cache_fixture: 'stub-app-dynamics-agent.zip' do
+
+          expect{component.compile}.to raise_error(RuntimeError, /AppDynamics configuration source dir/)
         end
       end
     end