diff --git a/test/api/Makefile.am b/test/api/Makefile.am
index ecf44754501c77e001fe7808f0bc372abdef6e12..e2e6166c00d6bcc32c32f79a511996a61e09e315 100644
--- a/test/api/Makefile.am
+++ b/test/api/Makefile.am
@@ -33,6 +33,7 @@ TEST_PROGS = \
 	test-shape \
 	test-subset-cmap \
 	test-subset-glyf \
+	test-subset-hdmx \
 	test-subset-hmtx \
 	test-subset-os2 \
 	test-unicode \
@@ -42,6 +43,7 @@ TEST_PROGS = \
 test_subset_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 test_subset_cmap_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 test_subset_glyf_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
+test_subset_hdmx_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 test_subset_hmtx_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 test_subset_os2_LDADD = $(LDADD) $(top_builddir)/src/libharfbuzz-subset.la
 
diff --git a/test/api/test-subset-hdmx.c b/test/api/test-subset-hdmx.c
new file mode 100644
index 0000000000000000000000000000000000000000..291eb7937fc87c61e65f6c11c07b1433ad50892b
--- /dev/null
+++ b/test/api/test-subset-hdmx.c
@@ -0,0 +1,81 @@
+/*
+ * Copyright © 2018  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Garret Rieger
+ */
+
+#include <stdbool.h>
+
+#include "hb-test.h"
+#include "hb-subset-test.h"
+
+/* Unit tests for hdmx subsetting */
+
+
+static void
+test_subset_hdmx_simple_subset (void)
+{
+  hb_face_t *face_abc = hb_subset_test_open_font ("fonts/Roboto-Regular.abc.ttf");
+  hb_face_t *face_ac = hb_subset_test_open_font ("fonts/Roboto-Regular.ac.ttf");
+
+  hb_set_t *codepoints = hb_set_create ();
+  hb_set_add (codepoints, 'a');
+  hb_set_add (codepoints, 'c');
+  hb_face_t *face_abc_subset = hb_subset_test_create_subset (face_abc, codepoints);
+  hb_set_destroy (codepoints);
+
+  hb_subset_test_check (face_ac, face_abc_subset, HB_TAG ('h','d','m','x'));
+
+  hb_face_destroy (face_abc_subset);
+  hb_face_destroy (face_abc);
+  hb_face_destroy (face_ac);
+}
+
+static void
+test_subset_hdmx_noop (void)
+{
+  hb_face_t *face_abc = hb_subset_test_open_font("fonts/Roboto-Regular.abc.ttf");
+
+  hb_set_t *codepoints = hb_set_create();
+  hb_set_add (codepoints, 'a');
+  hb_set_add (codepoints, 'b');
+  hb_set_add (codepoints, 'c');
+  hb_face_t *face_abc_subset = hb_subset_test_create_subset (face_abc, codepoints);
+  hb_set_destroy (codepoints);
+
+  hb_subset_test_check (face_abc, face_abc_subset, HB_TAG ('h','d','m','x'));
+
+  hb_face_destroy (face_abc_subset);
+  hb_face_destroy (face_abc);
+}
+
+int
+main (int argc, char **argv)
+{
+  hb_test_init (&argc, &argv);
+
+  hb_test_add (test_subset_hdmx_simple_subset);
+  hb_test_add (test_subset_hdmx_noop);
+
+  return hb_test_run();
+}