Subject: [PATCH 2/2] diff tests: rewrite flakyness-causing test "aid"

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Tue, 13 Apr 2021 14:28:34 +0200

If a new test is added to this "while read magic cmd" test facility
added in 3c2f75b590c (t4013: add tests for diff/log family output
options., 2006-06-26) but no test file is added it'll fail the first
time, but then succeed on subsequent runs as a new file has been added
in t4013.

Let's accomplish the same aim in way that doesn't cause subsequent
test runs to succeed. If we can't find the file we'll BUG out, and
suggest to the developer that they copy our "expect.new" file over,
unlike the previous "expect" file this won't be picked up on
subsequent runs.

Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
---
 t/t4013-diff-various.sh | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 67f6411aff9..228ff100c61 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -200,10 +200,12 @@ do
 	esac
 	test=$(echo "$label" | sed -e 's|[/ ][/ ]*|_|g')
 	pfx=$(printf "%04d" $test_count)
-	expect="$TEST_DIRECTORY/t4013/diff.$test"
+	expect_relative="t4013/diff.$test"
+	expect="$TEST_DIRECTORY/$expect_relative"
 	actual="$pfx-diff.$test"
 
 	test_expect_$status "git $cmd # magic is ${magic:-(not used)}" '
+		test_when_finished "rm $actual" &&
 		{
 			echo "$ git $cmd"
 			case "$magic" in
@@ -216,16 +218,19 @@ do
 			    -e "s/^\\(.*mixed; boundary=\"-*\\)$V\\(-*\\)\"\$/\\1g-i-t--v-e-r-s-i-o-n\2\"/"
 			echo "\$"
 		} >"$actual" &&
-		if test -f "$expect"
+
+		if ! test -f "$expect"
 		then
-			process_diffs "$actual" >actual &&
-			process_diffs "$expect" >expect &&
-			test_cmp expect actual
-		else
-			# this is to help developing new tests.
-			cp "$actual" "$expect"
-			false
-		fi
+			expect_new="$expect.new" &&
+			cp "$actual" "$expect_new" &&
+			BUG "Have no \"$expect_relative\", new test? The output is in \"$expect_new\", maybe use that?"
+		fi &&
+
+		test_when_finished "rm actual" &&
+		process_diffs "$actual" >actual &&
+		test_when_finished "rm expect" &&
+		process_diffs "$expect" >expect &&
+		test_cmp expect actual
 	'
 done <<\EOF
 diff-tree initial
-- 
2.31.1.646.g06d606cb9c7