t-reftable-merged: improve the test t_merged_single_record()

In t-reftable-merged.c, the test t_merged_single_record() ensures
that a ref ('a') which occurs in only one of the records ('r2')
can be retrieved. Improve this test by adding another record 'r3'
to ensure that ref 'a' only occurs in 'r2' and that merged tables
don't simply read the last record.

Mentored-by: Patrick Steinhardt <[email protected]>
Mentored-by: Christian Couder <[email protected]>
Signed-off-by: Chandra Pratap <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Chandra Pratap

t/unit-tests/t-reftable-merged.c

@@ -136,14 +136,19 @@ static void t_merged_single_record(void)
 		.update_index = 2,
 		.value_type = REFTABLE_REF_DELETION,
 	} };
+	struct reftable_ref_record r3[] = { {
+		.refname = (char *) "c",
+		.update_index = 3,
+		.value_type = REFTABLE_REF_DELETION,
+	} };
 
-	struct reftable_ref_record *refs[] = { r1, r2 };
-	size_t sizes[] = { ARRAY_SIZE(r1), ARRAY_SIZE(r2) };
-	struct strbuf bufs[2] = { STRBUF_INIT, STRBUF_INIT };
+	struct reftable_ref_record *refs[] = { r1, r2, r3 };
+	size_t sizes[] = { ARRAY_SIZE(r1), ARRAY_SIZE(r2), ARRAY_SIZE(r3) };
+	struct strbuf bufs[3] = { STRBUF_INIT, STRBUF_INIT, STRBUF_INIT };
 	struct reftable_block_source *bs = NULL;
 	struct reftable_reader **readers = NULL;
 	struct reftable_merged_table *mt =
-		merged_table_from_records(refs, &bs, &readers, sizes, bufs, 2);
+		merged_table_from_records(refs, &bs, &readers, sizes, bufs, 3);
 	struct reftable_ref_record ref = { 0 };
 	struct reftable_iterator it = { 0 };
 	int err;
@@ -157,7 +162,7 @@ static void t_merged_single_record(void)
 	check_int(ref.update_index, ==, 2);
 	reftable_ref_record_release(&ref);
 	reftable_iterator_destroy(&it);
-	readers_destroy(readers, 2);
+	readers_destroy(readers, 3);
 	reftable_merged_table_free(mt);
 	for (size_t i = 0; i < ARRAY_SIZE(bufs); i++)
 		strbuf_release(&bufs[i]);