1 files changed, 46 insertions, 0 deletions
diff --git a/lib/ccan/tally/test/run-mode.c b/lib/ccan/tally/test/run-mode.c
new file mode 100644
index 00000000000..cd2f2304436
--- /dev/null
+++ b/lib/ccan/tally/test/run-mode.c
@@ -0,0 +1,46 @@
+#include <ccan/tally/tally.c>
+#include <ccan/tap/tap.h>
+
+int main(void)
+{
+	int i;
+	struct tally *tally = tally_new(100);
+	ssize_t min, max, mode;
+	size_t err;
+
+	max = (ssize_t)~(1ULL << (sizeof(max)*CHAR_BIT - 1));
+	min = (ssize_t)(1ULL << (sizeof(max)*CHAR_BIT - 1));
+
+	plan_tests(100 + 50 + 100 + 100 + 10);
+	/* Simple mode test: should always be around 0 (we add that twice). */
+	for (i = 0; i < 100; i++) {
+		tally_add(tally, i);
+		tally_add(tally, -i);
+		mode = tally_approx_mode(tally, &err);
+		if (i < 50)
+			ok1(err == 0);
+		ok1(mode - (ssize_t)err <= 0 && mode + (ssize_t)err >= 0);
+	}
+
+	/* Works for big values too... */
+	for (i = 0; i < 100; i++) {
+		tally_add(tally, max - i);
+		tally_add(tally, min + 1 + i);
+		mode = tally_approx_mode(tally, &err);
+		ok1(mode - (ssize_t)err <= 0 && mode + (ssize_t)err >= 0);
+	}
+	free(tally);
+
+	tally = tally_new(10);
+	tally_add(tally, 0);
+	for (i = 0; i < 100; i++) {
+		tally_add(tally, i);
+		mode = tally_approx_mode(tally, &err);
+		if (i < 10)
+			ok1(err == 0);
+		ok1(mode - (ssize_t)err <= 0 && mode + (ssize_t)err >= 0);
+	}
+
+	free(tally);
+	return exit_status();
+}