Add unit test for ..get_start_of_next_voting_interval().

This functionality was covered only accidentally by our voting-test
code, and as such wasn't actually tested at all.  The tests that
called it made its coverage nondeterministic, depending on what time
of day you ran the tests.

Closes ticket 26014.

1 files changed, 64 insertions, 0 deletions

diff --git a/src/test/test_voting_schedule.c b/src/test/test_voting_schedule.c
new file mode 100644
index 0000000000..df6058b74f
--- /dev/null
+++ b/src/test/test_voting_schedule.c
@@ -0,0 +1,64 @@
+/* Copyright (c) 2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "orconfig.h"
+
+#include "or.h"
+#include "voting_schedule.h"
+
+#include "test.h"
+
+static void
+test_voting_schedule_interval_start(void *arg)
+{
+#define next_interval voting_schedule_get_start_of_next_interval
+  (void)arg;
+  char buf[ISO_TIME_LEN+1];
+
+  // Midnight UTC tonight (as I am writing this test)
+  const time_t midnight = 1525651200;
+  format_iso_time(buf, midnight);
+  tt_str_op(buf, OP_EQ, "2018-05-07 00:00:00");
+
+  /* Some simple tests with a 50-minute voting interval */
+
+  tt_i64_op(next_interval(midnight, 3000, 0), OP_EQ,
+            midnight+3000);
+
+  tt_i64_op(next_interval(midnight+100, 3000, 0), OP_EQ,
+            midnight+3000);
+
+  tt_i64_op(next_interval(midnight+3000, 3000, 0), OP_EQ,
+            midnight+6000);
+
+  tt_i64_op(next_interval(midnight+3001, 3000, 0), OP_EQ,
+            midnight+6000);
+
+  /* Make sure that we roll around properly at midnight */
+  tt_i64_op(next_interval(midnight+83000, 3000, 0), OP_EQ,
+            midnight+84000);
+
+  /* We start fresh at midnight UTC, even if there are leftover seconds. */
+  tt_i64_op(next_interval(midnight+84005, 3000, 0), OP_EQ,
+            midnight+86400);
+
+  /* Now try with offsets.  (These are only used for test networks.) */
+  tt_i64_op(next_interval(midnight, 3000, 99), OP_EQ,
+            midnight+99);
+
+  tt_i64_op(next_interval(midnight+100, 3000, 99), OP_EQ,
+            midnight+3099);
+
+ done:
+  ;
+#undef next_interval
+}
+
+#define VS(name,flags)                                          \
+  { #name, test_voting_schedule_##name, (flags), NULL, NULL }
+
+struct testcase_t voting_schedule_tests[] = {
+  VS(interval_start, 0),
+  END_OF_TESTCASES
+};
+