--- /dev/null
+#include <ccan/strset/strset.h>
+#include <ccan/strset/strset.c>
+#include <ccan/tap/tap.h>
+#include <stdio.h>
+
+/* Must be > 100, see below. */
+#define NUM 200
+
+static bool in_order(const char *value, unsigned int *count)
+{
+ int i = atoi(value);
+ ok1(*count == i);
+ (*count)++;
+ return false;
+}
+
+static bool find_empty(const char *value, char *empty)
+{
+ if (value == empty)
+ pass("Found empty entry!");
+ return false;
+}
+
+int main(void)
+{
+ struct strset set;
+ const struct strset *sub;
+ unsigned int i;
+ char *str[NUM], *empty;
+
+ plan_tests(7 + 1 + 10 + 100);
+ strset_init(&set);
+
+ for (i = 0; i < NUM; i++) {
+ char template[10];
+ sprintf(template, "%08u", i);
+ str[i] = strdup(template);
+ }
+
+ for (i = 0; i < NUM; i++)
+ strset_set(&set, str[i]);
+
+ /* Nothing */
+ sub = strset_prefix(&set, "a");
+ ok1(strset_empty(sub));
+
+ /* Everything */
+ sub = strset_prefix(&set, "0");
+ ok1(sub->u.n == set.u.n);
+ sub = strset_prefix(&set, "");
+ ok1(sub->u.n == set.u.n);
+
+ /* Singleton. */
+ sub = strset_prefix(&set, "00000000");
+ i = 0;
+ strset_iterate(sub, in_order, &i);
+ ok1(i == 1);
+
+ /* First 10. */
+ sub = strset_prefix(&set, "0000000");
+ i = 0;
+ strset_iterate(sub, in_order, &i);
+ ok1(i == 10);
+
+ /* First 100. */
+ sub = strset_prefix(&set, "000000");
+ i = 0;
+ strset_iterate(sub, in_order, &i);
+ ok1(i == 100);
+
+ /* Everything, *plus* empty string. */
+ empty = strdup("");
+ strset_set(&set, empty);
+
+ sub = strset_prefix(&set, "");
+ /* Check we get *our* empty string back! */
+ strset_iterate(sub, find_empty, empty);
+
+ strset_destroy(&set);
+
+ for (i = 0; i < NUM; i++)
+ free(str[i]);
+ free(empty);
+
+ /* This exits depending on whether all tests passed */
+ return exit_status();
+}