From 7fd7ebf3193773a1c8070b7d0e8eef26b7739444 Mon Sep 17 00:00:00 2001
From: Hugh Sorby <h.sorby@auckland.ac.nz>
Date: Mon, 9 Nov 2026 15:33:00 +1300
Subject: [PATCH] Add test for import of non-standard units.

---
 tests/importer/model_flattening.cpp           | 55 +++++++++++++++++++
 ...ort_for_import_for_nestedimportofunits.xml |  9 +++
 .../import_for_nestedimportofunits.xml        | 22 ++++++++
 .../modelflattening/nestedimportofunits.xml   |  9 +++
 .../units_for_nestedimportofunits.xml         | 17 ++++++
 5 files changed, 112 insertions(+)
 create mode 100644 tests/resources/modelflattening/import_for_import_for_nestedimportofunits.xml
 create mode 100644 tests/resources/modelflattening/import_for_nestedimportofunits.xml
 create mode 100644 tests/resources/modelflattening/nestedimportofunits.xml
 create mode 100644 tests/resources/modelflattening/units_for_nestedimportofunits.xml

diff --git a/tests/importer/model_flattening.cpp b/tests/importer/model_flattening.cpp
index f0e25d902b..59cedc613b 100644
--- a/tests/importer/model_flattening.cpp
+++ b/tests/importer/model_flattening.cpp
@@ -1940,3 +1940,58 @@ TEST(ModelFlattening, multiLayeredImportOfNonStandardUnits)
 
     EXPECT_NE(nullptr, flattenModel);
 }
+
+TEST(ModelFlattening, nestedImportOfUnitsWithNonStandardChildren)
+{
+    const std::string e =
+        "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+        "<model xmlns=\"http://www.cellml.org/cellml/2.0#\" name=\"main_model\">\n"
+        "  <units name=\"rate\">\n"
+        "    <unit units=\"mM\"/>\n"
+        "    <unit units=\"per_s\"/>\n"
+        "  </units>\n"
+        "  <units name=\"mM\">\n"
+        "    <unit prefix=\"milli\" units=\"mole\"/>\n"
+        "  </units>\n"
+        "  <units name=\"per_s\">\n"
+        "    <unit exponent=\"-1\" units=\"second\"/>\n"
+        "  </units>\n"
+        "  <units name=\"compound\">\n"
+        "    <unit units=\"rate\"/>\n"
+        "    <unit units=\"volt\"/>\n"
+        "  </units>\n"
+        "  <component name=\"parent\">\n"
+        "    <variable name=\"p\" units=\"rate\" interface=\"public_and_private\"/>\n"
+        "    <variable name=\"q\" units=\"compound\" interface=\"public\"/>\n"
+        "  </component>\n"
+        "  <component name=\"child\">\n"
+        "    <variable name=\"r\" units=\"rate\" interface=\"public\"/>\n"
+        "  </component>\n"
+        "  <connection component_1=\"parent\" component_2=\"child\">\n"
+        "    <map_variables variable_1=\"p\" variable_2=\"r\"/>\n"
+        "  </connection>\n"
+        "  <encapsulation>\n"
+        "    <component_ref component=\"parent\">\n"
+        "      <component_ref component=\"child\"/>\n"
+        "    </component_ref>\n"
+        "  </encapsulation>\n"
+        "</model>\n";
+
+    auto parser = libcellml::Parser::create();
+    auto model = parser->parseModel(fileContents("modelflattening/nestedimportofunits.xml"));
+    auto importer = libcellml::Importer::create();
+
+    EXPECT_TRUE(model->hasUnresolvedImports());
+    importer->resolveImports(model, resourcePath("modelflattening/"));
+    EXPECT_FALSE(model->hasUnresolvedImports());
+
+    model = importer->flattenModel(model);
+    EXPECT_EQ(size_t(0), importer->issueCount());
+
+    EXPECT_FALSE(model->hasUnits("rate_1"));
+
+    auto printer = libcellml::Printer::create();
+
+    auto a = printer->printModel(model);
+    EXPECT_EQ(e, a);
+}
diff --git a/tests/resources/modelflattening/import_for_import_for_nestedimportofunits.xml b/tests/resources/modelflattening/import_for_import_for_nestedimportofunits.xml
new file mode 100644
index 0000000000..3c3d5d2792
--- /dev/null
+++ b/tests/resources/modelflattening/import_for_import_for_nestedimportofunits.xml
@@ -0,0 +1,9 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<model xmlns="http://www.cellml.org/cellml/2.0#" xmlns:xlink="http://www.w3.org/1999/xlink" name="model_b">
+    <import xlink:href="units_for_nestedimportofunits.xml">
+        <units name="rate" units_ref="rate"/>
+    </import>
+    <component name="b_component">
+        <variable name="r" units="rate" interface="public"/>
+    </component>
+</model>
diff --git a/tests/resources/modelflattening/import_for_nestedimportofunits.xml b/tests/resources/modelflattening/import_for_nestedimportofunits.xml
new file mode 100644
index 0000000000..2fe8ebbec9
--- /dev/null
+++ b/tests/resources/modelflattening/import_for_nestedimportofunits.xml
@@ -0,0 +1,22 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<model xmlns="http://www.cellml.org/cellml/2.0#" xmlns:xlink="http://www.w3.org/1999/xlink" name="model_a">
+    <import xlink:href="units_for_nestedimportofunits.xml">
+        <units name="rate" units_ref="rate"/>
+        <units name="compound" units_ref="compound"/>
+    </import>
+    <import xlink:href="import_for_import_for_nestedimportofunits.xml">
+        <component component_ref="b_component" name="child"/>
+    </import>
+    <component name="parent">
+        <variable name="p" units="rate" interface="public_and_private"/>
+        <variable name="q" units="compound" interface="public"/>
+    </component>
+    <connection component_1="parent" component_2="child">
+        <map_variables variable_1="p" variable_2="r"/>
+    </connection>
+    <encapsulation>
+        <component_ref component="parent">
+            <component_ref component="child"/>
+        </component_ref>
+    </encapsulation>
+</model>
diff --git a/tests/resources/modelflattening/nestedimportofunits.xml b/tests/resources/modelflattening/nestedimportofunits.xml
new file mode 100644
index 0000000000..644b5dfa65
--- /dev/null
+++ b/tests/resources/modelflattening/nestedimportofunits.xml
@@ -0,0 +1,9 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<model xmlns="http://www.cellml.org/cellml/2.0#" xmlns:xlink="http://www.w3.org/1999/xlink" name="main_model">
+    <import xlink:href="units_for_nestedimportofunits.xml">
+        <units name="rate" units_ref="rate"/>
+    </import>
+    <import xlink:href="import_for_nestedimportofunits.xml">
+        <component component_ref="parent" name="parent"/>
+    </import>
+</model>
diff --git a/tests/resources/modelflattening/units_for_nestedimportofunits.xml b/tests/resources/modelflattening/units_for_nestedimportofunits.xml
new file mode 100644
index 0000000000..aa72bc4633
--- /dev/null
+++ b/tests/resources/modelflattening/units_for_nestedimportofunits.xml
@@ -0,0 +1,17 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<model xmlns="http://www.cellml.org/cellml/2.0#" name="units_model">
+    <units name="per_s">
+        <unit exponent="-1" units="second"/>
+    </units>
+    <units name="mM">
+        <unit prefix="milli" units="mole"/>
+    </units>
+    <units name="rate">
+        <unit units="mM"/>
+        <unit units="per_s"/>
+    </units>
+    <units name="compound">
+        <unit units="rate"/>
+        <unit units="volt"/>
+    </units>
+</model>