Run command with virtual X server

.circleci/config.yml

@@ -23,8 +23,8 @@ jobs:
                     - ~/.cargo
             - run: make test
             - run:
-                command: cargo run -- build
+                command: ./.circleci/xserver.sh cargo run -- build
                 working_directory: ~/md-pdf/test-files
             - run:
-                command: cargo run --release -- build
+                command: ./.circleci/xserver.sh cargo run --release -- build
                 working_directory: ~/md-pdf/test-files

.circleci/xserver.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+set -e
+
+xvfb-run -a --server-args="-screen 0 800x600x24" $@