Index: head/lib/libc/tests/stdlib/tsearch_test.c
===================================================================
--- head/lib/libc/tests/stdlib/tsearch_test.c	(revision 319612)
+++ head/lib/libc/tests/stdlib/tsearch_test.c	(revision 319613)
@@ -1,131 +1,159 @@
 /*-
  * Copyright (c) 2015 Nuxi, https://nuxi.nl/
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
 #include <atf-c.h>
 #define _SEARCH_PRIVATE
 #include <search.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <stdio.h>
 
+static int n_nodes = 0;
+static int n_seen = 0;
+
 /* Validates the integrity of an AVL tree. */
 static inline unsigned int
 tnode_assert(const posix_tnode *n)
 {
 	unsigned int height_left, height_right;
 	int balance;
 
 	if (n == NULL)
 		return 0;
 	height_left = tnode_assert(n->llink);
 	height_right = tnode_assert(n->rlink);
 	balance = (int)height_left - (int)height_right;
 	ATF_CHECK(balance >= -1);
 	ATF_CHECK(balance <= 1);
 	ATF_CHECK_EQ(balance, n->balance);
 	return (height_left > height_right ? height_left : height_right) + 1;
 }
 
 static int
 compar(const void *a, const void *b)
 {
 
 	return *(int *)a - *(int *)b;
 }
 
+static void
+treewalk(const posix_tnode *node, VISIT v, int level)
+{
+
+	if (v == postorder || v == leaf)
+		n_seen++;
+}
+
 ATF_TC_WITHOUT_HEAD(tsearch_test);
 ATF_TC_BODY(tsearch_test, tc)
 {
 	/*
 	 * Run the test below in a deterministic fashion to prevent this
 	 * test from potentially flapping. We assume that this provides
 	 * enough coverage.
 	 */
 #if 0
 	unsigned short random_state[3];
 	arc4random_buf(random_state, sizeof(random_state));
 #else
 	unsigned short random_state[3] = { 26554, 13330, 3246 };
 #endif
 
 #define NKEYS 1000
 	/* Create 1000 possible keys. */
 	int keys[NKEYS];
 	for (int i = 0; i < NKEYS; ++i)
 		keys[i] = i;
 
 	/* Apply random operations on a binary tree and check the results. */
 	posix_tnode *root = NULL;
 	bool present[NKEYS] = {};
 	for (int i = 0; i < NKEYS * 10; ++i) {
 		int key = nrand48(random_state) % NKEYS;
-		switch (nrand48(random_state) % 3) {
+		int sample = i;
+
+		/*
+		 * Ensure each case is tested at least 10 times, plus a
+		 * random sampling.
+		 */
+		if ((sample % NKEYS) > 3)
+			sample = nrand48(random_state) % 3;
+
+		switch (sample) {
 		case 0:  /* tdelete(). */
 			if (present[key]) {
 				ATF_CHECK(tdelete(&key, &root, compar) != NULL);
 				present[key] = false;
+				ATF_CHECK(n_nodes > 0);
+				n_nodes--;
 			} else {
 				ATF_CHECK_EQ(NULL,
 				    tdelete(&key, &root, compar));
 			}
 			break;
 		case 1:  /* tfind(). */
 			if (present[key]) {
 				ATF_CHECK_EQ(&keys[key],
 				    *(int **)tfind(&key, &root, compar));
 			} else {
 				ATF_CHECK_EQ(NULL, tfind(&key, &root, compar));
 			}
 			break;
 		case 2:  /* tsearch(). */
 			if (present[key]) {
 				ATF_CHECK_EQ(&keys[key],
 				    *(int **)tsearch(&key, &root, compar));
 			} else {
 				ATF_CHECK_EQ(&keys[key], *(int **)tsearch(
 				    &keys[key], &root, compar));
 				present[key] = true;
+				n_nodes++;
 			}
 			break;
 		}
 		tnode_assert(root);
 	}
+
+	/* Walk the tree. */
+	twalk(root, treewalk);
+	ATF_CHECK_EQ(n_nodes, n_seen);
 
 	/* Remove all entries from the tree. */
 	for (int key = 0; key < NKEYS; ++key)
 		if (present[key])
 			ATF_CHECK(tdelete(&key, &root, compar) != NULL);
 	ATF_CHECK_EQ(NULL, root);
 }
 
 ATF_TP_ADD_TCS(tp)
 {
 
 	ATF_TP_ADD_TC(tp, tsearch_test);
 
 	return (atf_no_error());
 }