tests: add dup.test, dup2.test, and dup3.test

* tests/dup.c: New file.
* tests/dup.test: New test.
* tests/dup2.c: New file.
* tests/dup2.test: New test.
* tests/dup3.c: New file.
* tests/dup3.test: New test.
* tests/.gitignore: Add dup, dup2, and dup3.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(TESTS): Add dup.test, dup2.test, and dup3.test.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 50902a6..f6d1c82 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -69,6 +69,9 @@
 	clock_nanosleep \
 	clock_xettime \
 	copy_file_range \
+	dup \
+	dup2 \
+	dup3 \
 	epoll_create1 \
 	eventfd \
 	execve \
@@ -235,6 +238,9 @@
 	clock_xettime.test \
 	copy_file_range.test \
 	dumpio.test \
+	dup.test \
+	dup2.test \
+	dup3.test \
 	epoll_create1.test \
 	eventfd.test \
 	execve.test \