2 files changed, 64 insertions, 0 deletions
diff --git a/tests/fs/test_mount.c b/tests/fs/test_mount.c
new file mode 100644
index 00000000..b1a337ad
--- /dev/null
+++ b/tests/fs/test_mount.c
@@ -0,0 +1,60 @@
+#include <assert.h>
+#include <stdio.h>
+#include <emscripten.h>
+
+int main() {
+  EM_ASM(
+    var ex;
+
+    // write a file that should be unaffected by this process
+    FS.writeFile('/safe.txt', 'abc');
+
+    // mount it the first time
+    FS.mkdir('/working');
+    FS.mount(MEMFS, {}, '/working');
+    FS.writeFile('/working/waka.txt', 'az');
+
+    // mount to a missing directory
+    try {
+      FS.mount(MEMFS, {}, '/missing');
+    } catch (e) {
+      ex = e;
+    }
+    assert(ex instanceof FS.ErrnoError && ex.errno === ERRNO_CODES.ENOENT);
+
+    // mount to an existing mountpoint
+    try {
+      FS.mount(MEMFS, {}, '/working');
+    } catch (e) {
+      ex = e;
+    }
+    assert(ex instanceof FS.ErrnoError && ex.errno === ERRNO_CODES.EBUSY);
+
+    // unmount
+    FS.unmount('/working');
+
+    // unmount something that's not mounted
+    try {
+      FS.unmount('/working');
+    } catch (e) {
+      ex = e;
+    }
+    assert(ex instanceof FS.ErrnoError && ex.errno === ERRNO_CODES.EINVAL);
+
+    // try to read the file from the old mount
+    try {
+      FS.readFile('/working/waka.txt', { encoding: 'utf8' });
+    } catch (e) {
+      ex = e;
+    }
+    assert(ex instanceof FS.ErrnoError && ex.errno === ERRNO_CODES.ENOENT);
+
+    // check the safe file
+    var contents = FS.readFile('/safe.txt', { encoding: 'utf8' });
+    assert(contents === 'abc');
+  );
+
+  puts("success");
+
+  return 0;
+}
diff --git a/tests/test_core.py b/tests/test_core.py
index 4d915e71..43b675f5 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -3957,6 +3957,10 @@ def process(filename):
       '''
     self.do_run(src, ('got: 35\ngot: 45\ngot: 25\ngot: 15\nisatty? 0,0,1\n', 'isatty? 0,0,1\ngot: 35\ngot: 45\ngot: 25\ngot: 15\n'), post_build=post)
 
+  def test_mount(self):
+    src = open(path_from_root('tests', 'fs', 'test_mount.c'), 'r').read()
+    self.do_run(src, 'success', force_c=True)
+
   def test_fwrite_0(self):
     test_path = path_from_root('tests', 'core', 'test_fwrite_0')
     src, output = (test_path + s for s in ('.in', '.out'))