1 files changed, 46 insertions, 0 deletions
diff --git a/lib/ccan/tally/test/run-median.c b/lib/ccan/tally/test/run-median.c
new file mode 100644
index 00000000000..b12fd8a021a
--- /dev/null
+++ b/lib/ccan/tally/test/run-median.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, median;
+	size_t err;
+
+	max = (ssize_t)~(1ULL << (sizeof(max)*CHAR_BIT - 1));
+	min = (ssize_t)(1ULL << (sizeof(max)*CHAR_BIT - 1));
+
+	plan_tests(100*2 + 100*2 + 100*2);
+	/* Simple median test: should always be around 0. */
+	for (i = 0; i < 100; i++) {
+		tally_add(tally, i);
+		tally_add(tally, -i);
+		median = tally_approx_median(tally, &err);
+		ok1(err <= 4);
+		ok1(median - (ssize_t)err <= 0 && median + (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);
+		median = tally_approx_median(tally, &err);
+		/* Error should be < 100th of max - min. */
+		ok1(err <= max / 100 * 2);
+		ok1(median - (ssize_t)err <= 0 && median + (ssize_t)err >= 0);
+	}
+	free(tally);
+
+	tally = tally_new(10);
+	for (i = 0; i < 100; i++) {
+		tally_add(tally, i);
+		median = tally_approx_median(tally, &err);
+		ok1(err <= i / 10 + 1);
+		ok1(median - (ssize_t)err <= i/2
+		    && median + (ssize_t)err >= i/2);
+	}
+	free(tally);
+
+	return exit_status();
+}