     test "http_proxy" do
       add_to_application_env(:http_proxy, "http://10.10.10.10:8888")
       assert valid_configuration |> Map.put(:http_proxy, "http://10.10.10.10:8888") == init_config
+      assert "http://10.10.10.10:8888" == System.get_env("APPSIGNAL_HTTP_PROXY")
     end
 
     test "ignore_actions" do
-      add_to_application_env(:ignore_actions, ~w(ExampleApplication.PageController#ignored))
-      assert valid_configuration |> Map.put(:ignore_actions, ~w(ExampleApplication.PageController#ignored)) == init_config
+      actions = ~w(
+          ExampleApplication.PageController#ignored
+          ExampleApplication.PageController#also_ignored
+      )
+      add_to_application_env(:ignore_actions, actions)
+      assert valid_configuration |> Map.put(:ignore_actions, actions) == init_config
+      assert "ExampleApplication.PageController#ignored,ExampleApplication.PageController#also_ignored" == System.get_env("APPSIGNAL_IGNORE_ACTIONS")
     end
 
     test "ignore_errors" do
-      add_to_application_env(:ignore_errors, ~w(VerySpecificError))
-      assert valid_configuration |> Map.put(:ignore_errors, ~w(VerySpecificError)) == init_config
+      errors = ~w(VerySpecificError AnotherError)
+      add_to_application_env(:ignore_errors, errors)
+      assert valid_configuration |> Map.put(:ignore_errors, errors) == init_config
+      assert "VerySpecificError,AnotherError" == System.get_env("APPSIGNAL_IGNORE_ERRORS")
     end
 
     test "enable_host_metrics" do
       add_to_application_env(:enable_host_metrics, true)
       assert valid_configuration |> Map.put(:enable_host_metrics, true) == init_config
+      assert "true" == System.get_env("APPSIGNAL_ENABLE_HOST_METRICS")
     end
 
     test "log" do

    test "log_path" do
      add_to_application_env(:log_path, "log/appsignal.log")
      assert valid_configuration |> Map.put(:log_path, "log/appsignal.log") == init_config
    end

    test "endpoint" do
      add_to_application_env(:endpoint, "https://push.staging.lol")
      assert valid_configuration |> Map.put(:endpoint, "https://push.staging.lol") == init_config
    end

    test "running_in_container" do
      add_to_application_env(:running_in_container, true)
      assert valid_configuration |> Map.put(:running_in_container, true) == init_config
    end

    test "send_params" do

    test "working_dir_path" do
      add_to_application_env(:working_dir_path, "/tmp/appsignal")
      assert valid_configuration |> Map.put(:working_dir_path, "/tmp/appsignal") == init_config
      assert "/tmp/appsignal" == System.get_env("APPSIGNAL_WORKING_DIR_PATH")
    end

    test "revision" do
      add_to_application_env(:revision, "03bd9e")
      assert valid_configuration |> Map.put(:revision, "03bd9e") == init_config
      assert "03bd9e" == System.get_env("APP_REVISION")
    end
  end

