diff --git a/src/Makefile.am b/src/Makefile.am
index 56dc32d9a..63eeff919 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -445,6 +445,7 @@ COMPILED_TESTS = \
 	test-vector \
 	test-repacker \
 	test-classdef-graph \
+	test-instancer-solver \
 	$(NULL)
 COMPILED_TESTS_CPPFLAGS = $(HBCFLAGS) -DMAIN -UNDEBUG
 COMPILED_TESTS_LDADD = libharfbuzz.la $(HBLIBS)
@@ -515,6 +516,10 @@ test_vector_SOURCES = test-vector.cc hb-static.cc
 test_vector_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
 test_vector_LDADD = $(COMPILED_TESTS_LDADD)
 
+test_instancer_solver_SOURCES = test-subset-instancer-solver.cc hb-subset-instancer-solver.cc hb-static.cc
+test_instancer_solver_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
+test_instancer_solver_LDADD = $(COMPILED_TESTS_LDADD)
+
 dist_check_SCRIPTS = \
 	check-c-linkage-decls.py \
 	check-externs.py \
diff --git a/src/hb-subset-instancer-solver.cc b/src/hb-subset-instancer-solver.cc
index bc1b37965..3484e203f 100644
--- a/src/hb-subset-instancer-solver.cc
+++ b/src/hb-subset-instancer-solver.cc
@@ -223,7 +223,7 @@ _solve (Triple tent, Triple axisLimit, bool negative = false)
 
       // Eternity justify.
       Triple loc2 {upper, axisMax, axisMax};
-      float scalar2 = 1.f; // supportScalar({"tag": axisMax}, {"tag": tent})
+      float scalar2 = supportScalar (axisMax, tent);
 
       out.push (hb_pair (scalar1 - gain, loc1));
       out.push (hb_pair (scalar2 - gain, loc2));
@@ -423,5 +423,5 @@ rebase_tent (Triple tent, Triple axisLimit)
 		       Triple{n (t.minimum), n (t.middle), n (t.maximum)}));
   }
 
-  return sols;
+  return out;
 }
diff --git a/src/meson.build b/src/meson.build
index 188f7712c..72772e9b6 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -701,6 +701,7 @@ if get_option('tests').enabled()
     'test-unicode-ranges': ['test-unicode-ranges.cc'],
     'test-vector': ['test-vector.cc', 'hb-static.cc'],
     'test-bimap': ['test-bimap.cc', 'hb-static.cc'],
+    'test-instancer-solver': ['test-subset-instancer-solver.cc', 'hb-subset-instancer-solver.cc', 'hb-static.cc'],
   }
   foreach name, source : compiled_tests
     if cpp.get_argument_syntax() == 'msvc' and source.contains('hb-static.cc')
diff --git a/src/test-subset-instancer-solver.cc b/src/test-subset-instancer-solver.cc
new file mode 100644
index 000000000..11de3aaf2
--- /dev/null
+++ b/src/test-subset-instancer-solver.cc
@@ -0,0 +1,351 @@
+/*
+ * Copyright © 2023  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): Qunxin Liu
+ */
+
+#include "hb-subset-instancer-solver.hh"
+
+static inline bool approx (Triple a, Triple b)
+{
+  return fabsf (a.minimum - b.minimum) < 0.000001f &&
+         fabsf (a.middle - b.middle) < 0.000001f &&
+         fabsf (a.maximum - b.maximum) < 0.000001f;
+}
+
+static inline bool approx (float a, float b)
+{ return fabsf (a - b) < 0.000001f; }
+
+/* tests ported from
+ * https://github.com/fonttools/fonttools/blob/main/Tests/varLib/instancer/solver_test.py */
+int
+main (int argc, char **argv)
+{
+  /* Case 1 */
+  {
+    /* pin axis*/
+    Triple tent (0.f, 1.f, 1.f);
+    Triple axis_range (0.f, 0.f, 0.f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 0);
+  }
+
+  {
+    /* pin axis*/
+    Triple tent (0.f, 1.f, 1.f);
+    Triple axis_range (0.5f, 0.5f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 0.5f);
+    assert (out[0].second == Triple ());
+  }
+
+  {
+    /* tent falls outside the new axis range */
+    Triple tent (0.3f, 0.5f, 0.8f);
+    Triple axis_range (0.1f, 0.2f, 0.3f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 0);
+  }
+
+  /* Case 2 */
+  {
+    Triple tent (0.f, 1.f, 1.f);
+    Triple axis_range (-1.f, 0.f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 0.5f);
+    assert (out[0].second == Triple (0.f, 1.f, 1.f));
+  }
+
+  /* Case 2 */
+  {
+    Triple tent (0.f, 1.f, 1.f);
+    Triple axis_range (-1.f, 0.f, 0.75f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 0.75f);
+    assert (out[0].second == Triple (0.f, 1.f, 1.f));
+  }
+
+  /* Without gain: */
+  /* Case 3 */
+  {
+    Triple tent (0.f, 0.2f, 1.f);
+    Triple axis_range (-1.f, 0.f, 0.8f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (0.f, 0.25f, 1.25f));
+  }
+
+  /* Case 3 boundary */
+  {
+    Triple tent (0.f, 0.4f, 1.f);
+    Triple axis_range (-1.f, 0.f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (0.f, 0.8f, 32767/(float) (1 << 14)));
+  }
+
+  /* Case 4 */
+  {
+    Triple tent (0.f, 0.25f, 1.f);
+    Triple axis_range (-1.f, 0.f, 0.4f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 2);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (0.f, 0.625f, 1.f));
+    assert (approx (out[1].first, 0.8f));
+    assert (out[1].second == Triple (0.625f, 1.f, 1.f));
+  }
+
+  /* Case 4 */
+  {
+    Triple tent (0.25f, 0.3f, 1.05f);
+    Triple axis_range (0.f, 0.2f, 0.4f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 2);
+    assert (out[0].first == 1.f);
+    assert (approx (out[0].second, Triple (0.25f, 0.5f, 1.f)));
+    assert (approx (out[1].first, 2.6f/3));
+    assert (approx (out[1].second, Triple (0.5f, 1.f, 1.f)));
+  }
+
+  /* Case 4 boundary */
+  {
+    Triple tent (0.25f, 0.5f, 1.f);
+    Triple axis_range (0.f, 0.25f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (0.f, 1.f, 1.f));
+  }
+
+  /* With gain */
+  /* Case 3a/1neg */
+  {
+    Triple tent (0.f, 0.5f, 1.f);
+    Triple axis_range (0.f, 0.5f, 1.f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 3);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+    assert (out[1].first == -1.f);
+    assert (out[1].second == Triple (0.f, 1.f, 1.f));
+    assert (out[2].first == -1.f);
+    assert (out[2].second == Triple (-1.f, -1.f, 0.f));
+  }
+
+  /* Case 3a/1neg */
+  {
+    Triple tent (0.f, 0.5f, 2.f);
+    Triple axis_range (0.2f, 0.5f, 0.8f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 3);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+    assert (approx (out[1].first, -0.2f));
+    assert (out[1].second == Triple (0.f, 1.f, 1.f));
+    assert (approx (out[2].first, -0.6f));
+    assert (out[2].second == Triple (-1.f, -1.f, 0.f));
+  }
+
+  /* Case 3a/1neg */
+  {
+    Triple tent (0.f, 0.5f, 2.f);
+    Triple axis_range (0.2f, 0.5f, 1.f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 3);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+    assert (approx (out[1].first, -1.f/3));
+    assert (out[1].second == Triple (0.f, 1.f, 1.f));
+    assert (approx (out[2].first, -0.6f));
+    assert (out[2].second == Triple (-1.f, -1.f, 0.f));
+  }
+
+  /* Case 3 */
+  {
+    Triple tent (0.f, 0.5f, 1.f);
+    Triple axis_range (0.25f, 0.25f, 0.75f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 3);
+    assert (out[0].first == 0.5f);
+    assert (out[0].second == Triple ());
+    assert (out[1].first == 0.5f);
+    assert (out[1].second == Triple (0.f, 0.5f, 1.5f));
+    assert (out[2].first == -0.5f);
+    assert (out[2].second == Triple (0.5f, 1.5f, 1.5f));
+  }
+
+  /* Case 1neg */
+  {
+    Triple tent (0.f, 0.5f, 1.f);
+    Triple axis_range (0.f, 0.25f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 3);
+    assert (out[0].first == 0.5f);
+    assert (out[0].second == Triple ());
+    assert (out[1].first == 0.5f);
+    assert (out[1].second == Triple (0.f, 1.f, 1.f));
+    assert (out[2].first == -0.5f);
+    assert (out[2].second == Triple (-1.f, -1.f, 0.f));
+  }
+
+  /* Case 2neg */
+  {
+    Triple tent (0.05f, 0.55f, 1.f);
+    Triple axis_range (0.f, 0.25f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 4);
+    assert (approx (out[0].first, 0.4f));
+    assert (out[0].second == Triple ());
+    assert (approx (out[1].first, 0.5f));
+    assert (out[1].second == Triple (0.f, 1.f, 1.f));
+    assert (approx (out[2].first, -0.4f));
+    assert (out[2].second == Triple (-1.f, -0.8f, 0.f));
+    assert (approx (out[3].first, -0.4f));
+    assert (out[3].second == Triple (-1.f, -1.f, -0.8f));
+  }
+
+  /* Case 2neg, other side */
+  {
+    Triple tent (-1.f, -0.55f, -0.05f);
+    Triple axis_range (-0.5f, -0.25f, 0.f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 4);
+    assert (approx (out[0].first, 0.4f));
+    assert (out[0].second == Triple ());
+    assert (approx (out[1].first, 0.5f));
+    assert (out[1].second == Triple (-1.f, -1.f, 0.f));
+    assert (approx (out[2].first, -0.4f));
+    assert (out[2].second == Triple (0.f, 0.8f, 1.f));
+    assert (approx (out[3].first, -0.4f));
+    assert (out[3].second == Triple (0.8f, 1.f, 1.f));
+  }
+
+  /* Misc corner cases */
+  {
+    Triple tent (0.5f, 0.5f, 0.5f);
+    Triple axis_range (0.5f, 0.5f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+  }
+
+  {
+    Triple tent (0.3f, 0.5f, 0.7f);
+    Triple axis_range (0.1f, 0.5f, 0.9f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 5);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+    assert (out[1].first == -1.f);
+    assert (out[1].second == Triple (0.f, 0.5f, 1.f));
+    assert (out[2].first == -1.f);
+    assert (out[2].second == Triple (0.5f, 1.f, 1.f));
+    assert (out[3].first == -1.f);
+    assert (approx (out[3].second, Triple (-1.f, -0.5f, 0.f)));
+    assert (out[4].first == -1.f);
+    assert (approx (out[4].second, Triple (-1.f, -1.f, -0.5f)));
+  }
+
+  {
+    Triple tent (0.5f, 0.5f, 0.5f);
+    Triple axis_range (0.25f, 0.25f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (1.f, 1.f, 1.f));
+  }
+
+  {
+    Triple tent (0.5f, 0.5f, 0.5f);
+    Triple axis_range (0.25f, 0.35f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (1.f, 1.f, 1.f));
+  }
+
+  {
+    Triple tent (0.5f, 0.5f, 0.55f);
+    Triple axis_range (0.25f, 0.35f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (1.f, 1.f, 1.f));
+  }
+
+  {
+    Triple tent (0.5f, 0.5f, 1.f);
+    Triple axis_range (0.5f, 0.5f, 1.f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 2);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+    assert (out[1].first == -1.f);
+    assert (out[1].second == Triple (0.f, 1.f, 1.f));
+  }
+
+  {
+    Triple tent (0.25f, 0.5f, 1.f);
+    Triple axis_range (0.5f, 0.5f, 1.f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 2);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+    assert (out[1].first == -1.f);
+    assert (out[1].second == Triple (0.f, 1.f, 1.f));
+  }
+
+  {
+    Triple tent (0.f, 0.2f, 1.f);
+    Triple axis_range (0.f, 0.f, 0.5f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 1);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple (0.f, 0.4f, 32767/(float) (1 << 14)));
+  }
+
+  {
+    Triple tent (0.5f, 0.5f, 0.5f);
+    Triple axis_range (0.f, 0.5f, 1.f);
+    result_t out = rebase_tent (tent, axis_range);
+    assert (out.length == 5);
+    assert (out[0].first == 1.f);
+    assert (out[0].second == Triple ());
+    assert (out[1].first == -1.f);
+    assert (out[1].second == Triple (0.f, 2/(float) (1 << 14), 1.f));
+    assert (out[2].first == -1.f);
+    assert (out[2].second == Triple (2/(float) (1 << 14), 1.f, 1.f));
+    assert (out[3].first == -1.f);
+    assert (out[3].second == Triple (-1.f, -2/(float) (1 << 14), 0.f));
+    assert (out[4].first == -1.f);
+    assert (out[4].second == Triple (-1.f, -1.f, -2/(float) (1 << 14)));
+  }
+}
+