Test BRIN autosummarization

There was no coverage for this code.

Reported-by: Nikolay Shaplov, Tom Lane
Discussion: https://postgr.es/m/2700647.XEouBYNZic@x200m
	https://postgr.es/m/13849.1506114543@sss.pgh.pa.us

src/test/modules/brin/Makefile

@@ -16,7 +16,7 @@ include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
 endif
 
-check: isolation-check
+check: isolation-check prove-check
 
 isolation-check: | submake-isolation
 	$(MKDIR_P) isolation_output
@@ -24,7 +24,10 @@ isolation-check: | submake-isolation
 	    --outputdir=./isolation_output \
 	    $(ISOLATIONCHECKS)
 
-.PHONY: check isolation-check
+prove-check:
+	$(prove_check)
+
+.PHONY: check isolation-check prove-check
 
 submake-isolation:
 	$(MAKE) -C $(top_builddir)/src/test/isolation all

src/test/modules/brin/t/01_workitems.pl

+# Verify that work items work correctly
+
+use strict;
+use warnings;
+
+use TestLib;
+use Test::More tests => 2;
+use PostgresNode;
+
+my $node = get_new_node('tango');
+$node->init;
+$node->append_conf('postgresql.conf', 'autovacuum_naptime=1s');
+$node->start;
+
+$node->safe_psql('postgres', 'create extension pageinspect');
+
+# Create a table with an autosummarizing BRIN index
+$node->safe_psql('postgres',
+	'create table brin_wi (a int) with (fillfactor = 10);
+	 create index brin_wi_idx on brin_wi using brin (a) with (pages_per_range=1, autosummarize=on);
+	 '
+);
+my $count = $node->safe_psql('postgres',
+	"select count(*) from brin_page_items(get_raw_page('brin_wi_idx', 2), 'brin_wi_idx'::regclass)"
+);
+is($count, '1', "initial index state is correct");
+
+$node->safe_psql('postgres',
+	'insert into brin_wi select * from generate_series(1, 100)');
+
+$node->poll_query_until('postgres',
+	"select count(*) > 1 from brin_page_items(get_raw_page('brin_wi_idx', 2), 'brin_wi_idx'::regclass)",
+	't');
+
+$count = $node->safe_psql('postgres',
+	"select count(*) > 1 from brin_page_items(get_raw_page('brin_wi_idx', 2), 'brin_wi_idx'::regclass)"
+);
+is($count, 't', "index got summarized");
+$node->stop;