diff --git a/src/Makefile.am b/src/Makefile.am
index 0f708a446f8..71b9f5def0e 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -443,6 +443,7 @@ COMPILED_TESTS = \
 	test-algs \
 	test-array \
 	test-bimap \
+	test-cff \
 	test-iter \
 	test-machinery \
 	test-map \
@@ -477,6 +478,10 @@ test_bimap_SOURCES = test-bimap.cc hb-static.cc
 test_bimap_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
 test_bimap_LDADD = $(COMPILED_TESTS_LDADD)
 
+test_cff_SOURCES = test-cff.cc hb-static.cc
+test_cff_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
+test_cff_LDADD = $(COMPILED_TESTS_LDADD)
+
 test_iter_SOURCES = test-iter.cc hb-static.cc
 test_iter_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
 test_iter_LDADD = $(COMPILED_TESTS_LDADD)
diff --git a/src/meson.build b/src/meson.build
index daa9198058c..8e4cea6ac5d 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -712,6 +712,7 @@ if get_option('tests').enabled()
     'test-algs': ['test-algs.cc', 'hb-static.cc'],
     'test-array': ['test-array.cc'],
     'test-bimap': ['test-bimap.cc', 'hb-static.cc'],
+    'test-cff': ['test-cff.cc', 'hb-static.cc'],
     'test-classdef-graph': ['graph/test-classdef-graph.cc', 'hb-static.cc', 'graph/gsubgpos-context.cc'],
     'test-iter': ['test-iter.cc', 'hb-static.cc'],
     'test-machinery': ['test-machinery.cc', 'hb-static.cc'],
diff --git a/src/test-cff.cc b/src/test-cff.cc
new file mode 100644
index 00000000000..38ddba3c496
--- /dev/null
+++ b/src/test-cff.cc
@@ -0,0 +1,75 @@
+/*
+ * Copyright © 2024  David Corbett
+ *
+ *  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.
+ */
+
+#include "hb.hh"
+#include "hb-ot-cff-common.hh"
+#include "hb-subset-cff-common.hh"
+
+int
+main (int argc, char **argv)
+{
+  /* Test encode_num_tp */
+  {
+    CFF::str_buff_t buff;
+    CFF::str_encoder_t encoder (buff);
+    CFF::number_t number;
+    struct num_tp_test {
+      double input;
+      unsigned length;
+      unsigned char output[7];
+    };
+    struct num_tp_test num_tp_tests[] = {
+      { -9.399999999999999, 4, { 0x1E, 0xE9, 0xA4, 0xFF } }, // -9.4
+      { 9.399999999999999999, 3, { 0x1E, 0x9A, 0x4F } }, // 9.4
+      { 456.8, 4, { 0x1E, 0x45, 0x6A, 0x8F } }, // 456.8
+      { 98765.37e2, 5, { 0x1E, 0x98, 0x76, 0x53, 0x7F } }, // 9876537
+      { 1234567890.0, 7, { 0x1E, 0x12, 0x34, 0x56, 0x79, 0xB2, 0xFF } }, // 12345679E2
+      { 9.876537e-4, 7, { 0x1E, 0x98, 0x76, 0x53, 0x7C, 0x10, 0xFF } }, // 9876537E-10
+      { 9.876537e4, 6, { 0x1E, 0x98, 0x76, 0x5A, 0x37, 0xFF } }, // 98765.37
+      { 1e8, 3, { 0x1E, 0x1B, 0x8F } }, // 1E8
+      { 1e-5, 3, { 0x1E, 0x1C, 0x5F } }, // 1E-5
+      { 1.2e8, 4, { 0x1E, 0x12, 0xB7, 0xFF } }, // 12E7
+      { 1.2345e-5, 5, { 0x1E, 0x12, 0x34, 0x5C, 0x9F } }, // 12345E-9
+      { 9.0987654e8, 6, { 0x1E, 0x90, 0x98, 0x76, 0x54, 0x0F } }, // 909876540
+      { 0.1, 3, { 0x1E, 0xA1, 0xFF } }, // .1
+      { -0.1, 3, { 0x1E, 0xEA, 0x1F } }, // -.1
+      { 0.01, 3, { 0x1E, 0x1C, 0x2F } }, // 1E-2
+      { -0.01, 4, { 0x1E, 0xE1, 0xC2, 0xFF } }, // -1E-2
+      { 0.0123, 4, { 0x1E, 0x12, 0x3C, 0x4F } }, // 123E-4
+      { -0.0123, 5, { 0x1E, 0xE1, 0x23, 0xC4, 0xFF } }, // -123E-4
+    };
+    for (size_t t = 0; t < sizeof num_tp_tests / sizeof num_tp_tests[0]; t++)
+    {
+      struct num_tp_test num_tp_test = num_tp_tests[t];
+      number.set_real (num_tp_test.input);
+      encoder.encode_num_tp (number);
+      assert (buff.length == num_tp_test.length);
+      for (unsigned i = 0; i < buff.length; i++)
+	assert (buff[i] == num_tp_test.output[i]);
+      encoder.reset ();
+    }
+  }
+
+  return 0;
+}