diff --git a/Dockerfile b/Dockerfile
index 35f3c3e6..5fb64ac2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -50,6 +50,7 @@ WORKDIR /home/docker
 
 ENV DEFAULT_RUFFUS_HISTORY_FILE=/tmp/.{basename}.ruffus_history.sqlite
 ENV OCRMYPDF_TEST_OUTPUT=/tmp/test-output
+ENV OCRMYPDF_IN_DOCKER=1
 
 # Must use array form of ENTRYPOINT
 # Non-array form does not append other arguments, because that is "intuitive"
diff --git a/ocrmypdf/test/test_pageinfo.py b/ocrmypdf/test/test_pageinfo.py
index ecb520ee..70f2fad6 100644
--- a/ocrmypdf/test/test_pageinfo.py
+++ b/ocrmypdf/test/test_pageinfo.py
@@ -7,7 +7,6 @@ from PIL import Image
 from tempfile import NamedTemporaryFile
 from contextlib import suppress
 import os
-import sys
 import shutil
 import pytest
 import img2pdf
@@ -15,7 +14,9 @@ from pkg_resources import Requirement, resource_filename
 
 req = Requirement.parse('ocrmypdf')
 
-TEST_OUTPUT = os.path.join(os.path.dirname(__file__), 'output')
+TEST_OUTPUT = os.environ.get(
+    'OCRMYPDF_TEST_OUTPUT',
+    default=os.path.join(os.path.dirname(__file__), 'output'))
 
 
 def setup_module():
diff --git a/tests/test_main.py b/tests/test_main.py
index 81de8336..d94e0ef6 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -265,6 +265,8 @@ def break_ghostscript_pdfa():
     return override_binary('gs', 'replace_ghostscript_nopdfa.py')
 
 
+@pytest.mark.skipif(os.environ.get('OCRMYPDF_IN_DOCKER', False),
+                    reason="Requires writable filesystem")
 def test_ghostscript_pdfa_fails(break_ghostscript_pdfa):
     env = os.environ.copy()
     env['PATH'] = break_ghostscript_pdfa
@@ -297,7 +299,7 @@ def test_blank_input_pdf():
 
 def test_french():
     p, out, err = run_ocrmypdf_env(
-        'français.pdf', 'français.pdf', '-l', 'fra')
+        'francais.pdf', 'francais.pdf', '-l', 'fra')
     assert p.returncode == ExitCode.ok, \
         "This test may fail if Tesseract language packs are missing"