test: Add closefrom() unit test

test/.gitignore

@@ -1,3 +1,4 @@
+closefrom
 endian
 fgetln
 funopen

test/Makefile.am

@@ -12,6 +12,7 @@ LDADD = $(top_builddir)/src/libbsd.la
 check_PROGRAMS = \
 	headers \
 	overlay \
+	closefrom \
 	endian \
 	humanize \
 	fgetln \

test/closefrom.c

@@ -0,0 +1,53 @@
+/*
+ * Copyright © 2015 Guillem Jover <guillem@hadrons.org>
+ *
+ * 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.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``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 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 <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+
+int
+main()
+{
+	int i;
+	int fd;
+
+	fd = open("/dev/null", O_RDONLY);
+
+	for (i = 4; i < 1024; i *= 2)
+		assert(dup2(fd, i) == i);
+
+	if (fd < 4)
+		close(fd);
+	closefrom(4);
+
+	for (i = 4; i < 1024; i++)
+		assert(fcntl(i, F_GETFL) == -1 && errno == EBADF);
+	assert(fcntl(fd, F_GETFL) == -1 && errno == EBADF);
+
+	return 0;
+}