diff --git a/LibOS/shim/test/fs/.gitignore b/LibOS/shim/test/fs/.gitignore
index efa23a46..3edece17 100644
--- a/LibOS/shim/test/fs/.gitignore
+++ b/LibOS/shim/test/fs/.gitignore
@@ -12,6 +12,7 @@
 /copy_whole
 /delete
 /open_close
+/open_flags
 /read_write
 /seek_tell
 /stat
diff --git a/LibOS/shim/test/fs/Makefile b/LibOS/shim/test/fs/Makefile
index 16a18d1b..820e204c 100644
--- a/LibOS/shim/test/fs/Makefile
+++ b/LibOS/shim/test/fs/Makefile
@@ -10,6 +10,7 @@ execs = \
 	$(copy_execs) \
 	delete \
 	open_close \
+	open_flags \
 	read_write \
 	seek_tell \
 	stat \
diff --git a/LibOS/shim/test/fs/open_flags.c b/LibOS/shim/test/fs/open_flags.c
new file mode 100644
index 00000000..1c22f87f
--- /dev/null
+++ b/LibOS/shim/test/fs/open_flags.c
@@ -0,0 +1,83 @@
+#include "common.h"
+
+const int g_mode = 0664;
+const char g_data = 'x';
+
+size_t get_file_size(const char* path) {
+    struct stat st;
+    if (stat(path, &st) < 0)
+        fatal_error("Failed to stat file '%s': %s\n", path, strerror(errno));
+    printf("size(%s) == %zu\n", path, st.st_size);
+    return st.st_size;
+}
+
+void open_test__(const char* path, int flags, const char* flags_str, bool exists,
+                 bool expect_success, bool do_write) {
+    const char* exists_str = exists ? "exists" : "doesn't exist";
+    int fd = open(path, flags, g_mode);
+    if (fd < 0) {
+        if (expect_success) {
+            fatal_error("open(%s) [%s] failed!\n", flags_str, exists_str);
+        } else {
+            printf("open(%s) [%s] failed as expected\n", flags_str, exists_str);
+        }
+    } else {
+        if (expect_success) {
+            printf("open(%s) [%s] succeeded as expected\n", flags_str, exists_str);
+            if (do_write)
+                write_fd(path, fd, &g_data, sizeof(g_data));
+        } else {
+            fatal_error("open(%s) [%s] unexpectedly succeeded\n", flags_str, exists_str);
+        }
+        close(fd);
+    }
+}
+
+#define OPEN_TEST(path, flags, exists, expect_success, do_write) \
+    open_test__(path, flags, #flags, exists, expect_success, do_write)
+
+int main(int argc, char* argv[]) {
+    if (argc < 2)
+        fatal_error("Usage: %s <path>\n", argv[0]);
+
+    setup();
+
+    // doesn't exist - should create
+    OPEN_TEST(argv[1], O_CREAT|O_EXCL|O_RDWR, /*exists=*/false, /*expect_success=*/true,
+              /*do_write=*/true);
+
+    // exists - open should fail
+    OPEN_TEST(argv[1], O_CREAT|O_EXCL|O_RDWR, /*exists=*/true, /*expect_success=*/false,
+              /*do_write=*/false);
+
+    // exists - should open existing and NOT truncate
+    OPEN_TEST(argv[1], O_CREAT|O_RDWR, /*exists=*/true, /*expect_success=*/true,
+              /*do_write=*/false);
+    if (get_file_size(argv[1]) != 1)
+        fatal_error("File was truncated\n");
+
+    if (unlink(argv[1]) < 0)
+        fatal_error("unlink(%s) failed: %s\n", argv[1], strerror(errno));
+
+    // doesn't exist - should create new
+    OPEN_TEST(argv[1], O_CREAT|O_RDWR, /*exists=*/false, /*expect_success=*/true,
+              /*do_write=*/false);
+
+    if (unlink(argv[1]) < 0)
+        fatal_error("unlink(%s) failed: %s\n", argv[1], strerror(errno));
+
+    // doesn't exist - should create new
+    OPEN_TEST(argv[1], O_CREAT|O_TRUNC|O_RDWR, /*exists=*/false, /*expect_success=*/true,
+              /*do_write=*/true);
+
+    // exists - should truncate
+    OPEN_TEST(argv[1], O_CREAT|O_TRUNC|O_RDWR, /*exists=*/true, /*expect_success=*/true,
+              /*do_write=*/false);
+    if (get_file_size(argv[1]) != 0)
+        fatal_error("File was not truncated\n");
+
+    if (unlink(argv[1]) < 0)
+        fatal_error("unlink(%s) failed: %s\n", argv[1], strerror(errno));
+
+    return 0;
+}
diff --git a/LibOS/shim/test/fs/test_fs.py b/LibOS/shim/test/fs/test_fs.py
index 6a363422..de25f9e1 100644
--- a/LibOS/shim/test/fs/test_fs.py
+++ b/LibOS/shim/test/fs/test_fs.py
@@ -79,6 +79,20 @@ class TC_00_FileSystem(RegressionTestCase):
         stdout, stderr = self.run_binary(['open_close', input_path, output_path])
         self.verify_open_close(stdout, stderr, input_path, output_path)
 
+    def verify_open_flags(self, stdout, stderr):
+        self.assertNotIn('ERROR: ', stderr)
+        self.assertIn('open(O_CREAT|O_EXCL|O_RDWR) [doesn\'t exist] succeeded as expected', stdout)
+        self.assertIn('open(O_CREAT|O_EXCL|O_RDWR) [exists] failed as expected', stdout)
+        self.assertIn('open(O_CREAT|O_RDWR) [exists] succeeded as expected', stdout)
+        self.assertIn('open(O_CREAT|O_RDWR) [doesn\'t exist] succeeded as expected', stdout)
+        self.assertIn('open(O_CREAT|O_TRUNC|O_RDWR) [doesn\'t exist] succeeded as expected', stdout)
+        self.assertIn('open(O_CREAT|O_TRUNC|O_RDWR) [exists] succeeded as expected', stdout)
+
+    def test_101_open_flags(self):
+        file_path = os.path.join(self.OUTPUT_DIR, 'test_101') # new file to be created
+        stdout, stderr = self.run_binary(['open_flags', file_path])
+        self.verify_open_flags(stdout, stderr)
+
     def test_110_read_write(self):
         file_path = os.path.join(self.OUTPUT_DIR, 'test_110') # new file to be created
         stdout, stderr = self.run_binary(['read_write', file_path])