From 8defa11c4784b6e1a1c1a745b022b95c6956378c Mon Sep 17 00:00:00 2001
From: Guillaume Ayoub <guillaume@courtbouillon.org>
Date: Sat, 12 Dec 2020 15:17:41 +0100
Subject: [PATCH] Make tests fail when an error is reported by GhostScript

---
 tests/conftest.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/conftest.py b/tests/conftest.py
index 21761dd5..634f73c7 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -29,6 +29,10 @@ def document_write_png(self, target=None, resolution=96, antialiasing=1):
         f'-r{resolution}', '-sOutputFile=-', '-']
     pngs = run(command, input=pdf, stdout=PIPE).stdout
 
+    assert pngs.startswith(MAGIC_NUMBER), (
+        'GhostScript error: '
+        f'{pngs.split(MAGIC_NUMBER)[0].decode("ascii").strip()}')
+
     # TODO: use a different way to find PNG files in stream
     magic_numbers = pngs.count(MAGIC_NUMBER)
     if magic_numbers == 1: