diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index cc4b10236e2..e568156ca83 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -328,7 +328,7 @@ test_expect_success 'git branch --list -v with --abbrev' '
 '
 
 test_expect_success 'git branch --column' '
-	COLUMNS=81 git branch --column=column >actual &&
+	test_with_columns 81 git branch --column=column >actual &&
 	cat >expect <<\EOF &&
   a/b/c   bam     foo     l     * main    n       o/p     r
   abc     bar     j/k     m/m     mb      o/o     q       topic
@@ -341,7 +341,7 @@ test_expect_success 'git branch --column with an extremely long branch name' '
 	long=z$long/$long/$long/$long &&
 	test_when_finished "git branch -d $long" &&
 	git branch $long &&
-	COLUMNS=80 git branch --column=column >actual &&
+	test_with_columns 80 git branch --column=column >actual &&
 	cat >expect <<EOF &&
   a/b/c
   abc
@@ -367,7 +367,7 @@ EOF
 test_expect_success 'git branch with column.*' '
 	git config column.ui column &&
 	git config column.branch "dense" &&
-	COLUMNS=80 git branch >actual &&
+	test_with_columns 80 git branch >actual &&
 	git config --unset column.branch &&
 	git config --unset column.ui &&
 	cat >expect <<\EOF &&
@@ -383,7 +383,7 @@ test_expect_success 'git branch --column -v should fail' '
 
 test_expect_success 'git branch -v with column.ui ignored' '
 	git config column.ui column &&
-	COLUMNS=80 git branch -v | cut -c -8 | sed "s/ *$//" >actual &&
+	test_with_columns 80 git branch -v | cut -c -8 | sed "s/ *$//" >actual &&
 	git config --unset column.ui &&
 	cat >expect <<\EOF &&
   a/b/c
diff --git a/t/t4052-stat-output.sh b/t/t4052-stat-output.sh
index 9eba436211f..3a91df50dd8 100755
--- a/t/t4052-stat-output.sh
+++ b/t/t4052-stat-output.sh
@@ -111,7 +111,7 @@ cat >expect72 <<'EOF'
  abcd | 1000 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 EOF
 test_expect_success "format-patch --cover-letter ignores COLUMNS (big change)" '
-	COLUMNS=200 git format-patch -1 --stdout --cover-letter >output &&
+	test_with_columns 200 git format-patch -1 --stdout --cover-letter >output &&
 	grep " | " output >actual &&
 	test_cmp expect72 actual
 '
@@ -131,7 +131,7 @@ EOF
 while read verb expect cmd args
 do
 	test_expect_success "$cmd $verb COLUMNS (big change)" '
-		COLUMNS=200 git $cmd $args >output &&
+		test_with_columns 200 git $cmd $args >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect" actual
 	'
@@ -139,7 +139,7 @@ do
 	case "$cmd" in diff|show) continue;; esac
 
 	test_expect_success "$cmd --graph $verb COLUMNS (big change)" '
-		COLUMNS=200 git $cmd $args --graph >output &&
+		test_with_columns 200 git $cmd $args --graph >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect-graph" actual
 	'
@@ -159,7 +159,7 @@ EOF
 while read verb expect cmd args
 do
 	test_expect_success "$cmd $verb not enough COLUMNS (big change)" '
-		COLUMNS=40 git $cmd $args >output &&
+		test_with_columns 40 git $cmd $args >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect" actual
 	'
@@ -167,7 +167,7 @@ do
 	case "$cmd" in diff|show) continue;; esac
 
 	test_expect_success "$cmd --graph $verb not enough COLUMNS (big change)" '
-		COLUMNS=40 git $cmd $args --graph >output &&
+		test_with_columns 40 git $cmd $args --graph >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect-graph" actual
 	'
@@ -302,7 +302,7 @@ EOF
 while read verb expect cmd args
 do
 	test_expect_success "$cmd $verb COLUMNS (long filename)" '
-		COLUMNS=200 git $cmd $args >output &&
+		test_with_columns 200 git $cmd $args >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect" actual
 	'
@@ -310,7 +310,7 @@ do
 	case "$cmd" in diff|show) continue;; esac
 
 	test_expect_success "$cmd --graph $verb COLUMNS (long filename)" '
-		COLUMNS=200 git $cmd $args --graph >output &&
+		test_with_columns 200 git $cmd $args --graph >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect-graph" actual
 	'
@@ -331,7 +331,7 @@ while read verb expect cmd args
 do
 	test_expect_success COLUMNS_CAN_BE_1 \
 		"$cmd $verb prefix greater than COLUMNS (big change)" '
-		COLUMNS=1 git $cmd $args >output &&
+		test_with_columns 1 git $cmd $args >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect" actual
 	'
@@ -340,7 +340,7 @@ do
 
 	test_expect_success COLUMNS_CAN_BE_1 \
 		"$cmd --graph $verb prefix greater than COLUMNS (big change)" '
-		COLUMNS=1 git $cmd $args --graph >output &&
+		test_with_columns 1 git $cmd $args --graph >output &&
 		grep " | " output >actual &&
 		test_cmp "$expect-graph" actual
 	'
@@ -356,7 +356,7 @@ cat >expect <<'EOF'
 EOF
 test_expect_success 'merge --stat respects COLUMNS (big change)' '
 	git checkout -b branch HEAD^^ &&
-	COLUMNS=100 git merge --stat --no-ff main^ >output &&
+	test_with_columns 100 git merge --stat --no-ff main^ >output &&
 	grep " | " output >actual &&
 	test_cmp expect actual
 '
@@ -365,7 +365,7 @@ cat >expect <<'EOF'
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa | 1000 +++++++++++++++++++++++++++++++++++++++
 EOF
 test_expect_success 'merge --stat respects COLUMNS (long filename)' '
-	COLUMNS=100 git merge --stat --no-ff main >output &&
+	test_with_columns 100 git merge --stat --no-ff main >output &&
 	grep " | " output >actual &&
 	test_cmp expect actual
 '
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 5865daa8f8d..a035f749537 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -207,7 +207,7 @@ test_expect_success 'left alignment formatting at the nth column' '
 '
 
 test_expect_success 'left alignment formatting at the nth column' '
-	COLUMNS=50 git log --pretty="tformat:%h %<|(-10)%s" >actual &&
+	test_with_columns 50 git log --pretty="tformat:%h %<|(-10)%s" >actual &&
 	qz_to_tab_space <<-EOF >expected &&
 	$head1 message two                    Z
 	$head2 message one                    Z
@@ -350,7 +350,7 @@ test_expect_success 'right alignment formatting at the nth column' '
 '
 
 test_expect_success 'right alignment formatting at the nth column' '
-	COLUMNS=50 git log --pretty="tformat:%h %>|(-10)%s" >actual &&
+	test_with_columns 50 git log --pretty="tformat:%h %>|(-10)%s" >actual &&
 	qz_to_tab_space <<-EOF >expected &&
 	$head1                      message two
 	$head2                      message one
@@ -450,7 +450,7 @@ test_expect_success 'center alignment formatting at the nth column' '
 '
 
 test_expect_success 'center alignment formatting at the nth column' '
-	COLUMNS=70 git log --pretty="tformat:%h %><|(-30)%s" >actual &&
+	test_with_columns 70 git log --pretty="tformat:%h %><|(-30)%s" >actual &&
 	qz_to_tab_space <<-EOF >expected &&
 	$head1           message two          Z
 	$head2           message one          Z
diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index 2f72c5c6883..e893c43d705 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -372,7 +372,7 @@ test_expect_success 'tag -l <pattern> -l <pattern> works, as our buggy documenta
 '
 
 test_expect_success 'listing tags in column' '
-	COLUMNS=41 git tag -l --column=row >actual &&
+	test_with_columns 41 git tag -l --column=row >actual &&
 	cat >expected <<\EOF &&
 a1      aa1     cba     t210    t211
 v0.2.1  v1.0    v1.0.1  v1.1.3
@@ -383,7 +383,7 @@ EOF
 test_expect_success 'listing tags in column with column.*' '
 	test_config column.tag row &&
 	test_config column.ui dense &&
-	COLUMNS=40 git tag -l >actual &&
+	test_with_columns 40 git tag -l >actual &&
 	cat >expected <<\EOF &&
 a1      aa1   cba     t210    t211
 v0.2.1  v1.0  v1.0.1  v1.1.3
@@ -397,7 +397,7 @@ test_expect_success 'listing tag with -n --column should fail' '
 
 test_expect_success 'listing tags -n in column with column.ui ignored' '
 	test_config column.ui "row dense" &&
-	COLUMNS=40 git tag -l -n >actual &&
+	test_with_columns 40 git tag -l -n >actual &&
 	cat >expected <<\EOF &&
 a1              Foo
 aa1             Foo
diff --git a/t/t7006-pager.sh b/t/t7006-pager.sh
index 0e7cf75435e..5189699debf 100755
--- a/t/t7006-pager.sh
+++ b/t/t7006-pager.sh
@@ -651,7 +651,7 @@ test_expect_success TTY 'git tag with auto-columns ' '
 	cat >expect <<-\EOF &&
 	initial  one      two      three    four     five
 	EOF
-	test_terminal env PAGER="cat >actual" COLUMNS=80 \
+	test_with_columns 80 test_terminal env PAGER="cat >actual" \
 		git -c column.ui=auto tag --sort=authordate &&
 	test_cmp expect actual
 '
diff --git a/t/t7508-status.sh b/t/t7508-status.sh
index 2b72451ba3e..808b8f50576 100755
--- a/t/t7508-status.sh
+++ b/t/t7508-status.sh
@@ -108,13 +108,13 @@ test_expect_success 'status --column' '
 #	dir2/modified  untracked
 #
 EOF
-	COLUMNS=50 git -c status.displayCommentPrefix=true status --column="column dense" >output &&
+	test_with_columns 50 git -c status.displayCommentPrefix=true status --column="column dense" >output &&
 	test_cmp expect output
 '
 
 test_expect_success 'status --column status.displayCommentPrefix=false' '
 	strip_comments expect &&
-	COLUMNS=49 git -c status.displayCommentPrefix=false status --column="column dense" >output &&
+	test_with_columns 49 git -c status.displayCommentPrefix=false status --column="column dense" >output &&
 	test_cmp expect output
 '
 
diff --git a/t/t9002-column.sh b/t/t9002-column.sh
index 89983527b62..9151d69bcf1 100755
--- a/t/t9002-column.sh
+++ b/t/t9002-column.sh
@@ -46,7 +46,7 @@ test_expect_success '80 columns' '
 	cat >expected <<\EOF &&
 one    two    three  four   five   six    seven  eight  nine   ten    eleven
 EOF
-	COLUMNS=80 git column --mode=column <lista >actual &&
+	test_with_columns 80 git column --mode=column <lista >actual &&
 	test_cmp expected actual
 '
 
@@ -65,7 +65,7 @@ eleven
 EOF
 
 test_expect_success COLUMNS_CAN_BE_1 'COLUMNS = 1' '
-	COLUMNS=1 git column --mode=column <lista >actual &&
+	test_with_columns 1 git column --mode=column <lista >actual &&
 	test_cmp expected actual
 '
 
@@ -74,9 +74,6 @@ test_expect_success 'width = 1' '
 	test_cmp expected actual
 '
 
-COLUMNS=20
-export COLUMNS
-
 test_expect_success '20 columns' '
 	cat >expected <<\EOF &&
 one    seven
@@ -86,7 +83,7 @@ four   ten
 five   eleven
 six
 EOF
-	git column --mode=column <lista >actual &&
+	test_with_columns 20 git column --mode=column <lista >actual &&
 	test_cmp expected actual
 '
 
@@ -99,7 +96,7 @@ four   ten
 five   eleven
 six
 EOF
-	git column --mode=column,nodense < lista > actual &&
+	test_with_columns 20 git column --mode=column,nodense < lista > actual &&
 	test_cmp expected actual
 '
 
@@ -110,7 +107,7 @@ two   six   ten
 three seven eleven
 four  eight
 EOF
-	git column --mode=column,dense < lista > actual &&
+	test_with_columns 20 git column --mode=column,dense < lista > actual &&
 	test_cmp expected actual
 '
 
@@ -123,7 +120,7 @@ four    ten
 five    eleven
 six
 EOF
-	git column --mode=column --padding 2 <lista >actual &&
+	test_with_columns 20 git column --mode=column --padding 2 <lista >actual &&
 	test_cmp expected actual
 '
 
@@ -136,7 +133,7 @@ test_expect_success '20 columns, indented' '
   five   eleven
   six
 EOF
-	git column --mode=column --indent="  " <lista >actual &&
+	test_with_columns 20 git column --mode=column --indent="  " <lista >actual &&
 	test_cmp expected actual
 '
 
@@ -149,7 +146,7 @@ seven  eight
 nine   ten
 eleven
 EOF
-	git column --mode=row <lista >actual &&
+	test_with_columns 20 git column --mode=row <lista >actual &&
 	test_cmp expected actual
 '
 
@@ -162,7 +159,7 @@ seven  eight
 nine   ten
 eleven
 EOF
-	git column --mode=row,nodense <lista >actual &&
+	test_with_columns 20 git column --mode=row,nodense <lista >actual &&
 	test_cmp expected actual
 '
 
@@ -173,7 +170,7 @@ four  five   six
 seven eight  nine
 ten   eleven
 EOF
-	git column --mode=row,dense <lista >actual &&
+	test_with_columns 20 git column --mode=row,dense <lista >actual &&
 	test_cmp expected actual
 '
 
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 37da7d9a99a..536339faaa2 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1718,3 +1718,11 @@ test_region () {
 test_readlink () {
 	perl -le 'print readlink($_) for @ARGV' "$@"
 }
+
+# Test a with a given number of COLUMNS in the environment.
+test_with_columns () {
+	local columns=$1
+	shift
+
+	COLUMNS=$columns "$@"
+}
