From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 15 Jun 2022 19:42:23 +0200
Subject: [PATCH v7 1/6] Use Test::Differences if available

---
 src/test/modules/libpq_pipeline/README              |  3 +++
 .../modules/libpq_pipeline/t/001_libpq_pipeline.pl  | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/test/modules/libpq_pipeline/README b/src/test/modules/libpq_pipeline/README
index d8174dd579..59c6ea8109 100644
--- a/src/test/modules/libpq_pipeline/README
+++ b/src/test/modules/libpq_pipeline/README
@@ -1 +1,4 @@
 Test programs and libraries for libpq
+
+If you have Test::Differences installed, any differences in the trace files
+are displayed in a format that's easier to read than the standard format.
diff --git a/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
index d8d496c995..49eec8a63a 100644
--- a/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
+++ b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
@@ -9,6 +9,17 @@ use PostgresNode;
 use TestLib;
 use Test::More;
 
+# Use Test::Differences if installed, and select unified diff output.
+# No decent way to select a context line count with this;
+# we could use a sub ref to allow that.
+BEGIN
+{
+	if (!eval q{ use Test::Differences; unified_diff(); 1 })
+	{
+		*eq_or_diff = \&is;
+	}
+}
+
 my $node = get_new_node('main');
 $node->init;
 $node->start;
@@ -54,7 +65,7 @@ for my $testname (@tests)
 		$result = slurp_file_eval($traceout);
 		next unless $result ne "";
 
-		is($result, $expected, "$testname trace match");
+		eq_or_diff($result, $expected, "$testname trace match");
 	}
 }
 
-- 
2.30.2


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