diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -785,6 +785,7 @@ def main():
     os.environ['TZ'] = 'GMT'
     os.environ["EMAIL"] = "Foo Bar <foo.bar@example.com>"
     os.environ['CDPATH'] = ''
+    os.environ['COLUMNS'] = '80'
 
     global TESTDIR, HGTMP, INST, BINDIR, PYTHONDIR, COVERAGE_FILE
     TESTDIR = os.environ["TESTDIR"] = os.getcwd()
diff --git a/tests/test-churn b/tests/test-churn
--- a/tests/test-churn
+++ b/tests/test-churn
@@ -3,8 +3,6 @@
 echo "[extensions]" >> $HGRCPATH
 echo "churn=" >> $HGRCPATH
 
-COLUMNS=80; export COLUMNS
-
 echo % create test repository
 hg init repo
 cd repo
diff --git a/tests/test-patchbomb b/tests/test-patchbomb
--- a/tests/test-patchbomb
+++ b/tests/test-patchbomb
@@ -12,8 +12,6 @@ fixheaders()
 echo "[extensions]" >> $HGRCPATH
 echo "patchbomb=" >> $HGRCPATH
 
-COLUMNS=80; export COLUMNS
-
 hg init t
 cd t
 echo a > a