add tests for library interface and python

unittest/c-library/test_library_objects.cpp

@@ -213,3 +213,23 @@ TEST_F(LibraryObjects, variables)
 
     LAMMPS_NS::platform::unlink("test_variable.file");
 }
+
+TEST_F(LibraryObjects, expand)
+{
+    ::testing::internal::CaptureStdout();
+    lammps_command(lmp, "variable one    index     1 2 3 4");
+    lammps_command(lmp, "variable two    equal     2");
+    lammps_command(lmp, "variable three  string    three");
+    std::string output = ::testing::internal::GetCapturedStdout();
+    if (verbose) std::cout << output;
+
+    char *ptr = lammps_expand(lmp, "xx_$(4+5)_$(PI) ${one}-${two}-${three}");
+    EXPECT_NE(ptr, nullptr);
+    EXPECT_THAT((char *)ptr, StrEq("xx_9_3.141592653589793116 1-2-three"));
+    lammps_free(ptr);
+
+    ptr = lammps_expand(lmp, "'xx_$(4+5)_$(PI) ${one}-${two}-${three}'");
+    EXPECT_NE(ptr, nullptr);
+    EXPECT_THAT((char *)ptr, StrEq("'xx_$(4+5)_$(PI) ${one}-${two}-${three}'"));
+    lammps_free(ptr);
+}

unittest/python/python-commands.py

@@ -528,6 +528,16 @@ create_atoms 1 single &
         self.assertEqual(a[0], x[0]*x[0]+x[1]*x[1]+x[2]*x[2])
         self.assertEqual(a[1], x[3]*x[3]+x[4]*x[4]+x[5]*x[5])
 
+    def test_expand(self):
+        self.lmp.command("variable one    index     1 2 3 4");
+        self.lmp.command("variable two    equal     2");
+        self.lmp.command("variable three  string    three");
+
+        expanded = self.lmp.expand("xx_$(4+5)_$(PI) ${one}-${two}-${three}")
+        self.assertEqual(expanded, "xx_9_3.141592653589793116 1-2-three")
+        expanded = self.lmp.expand("'xx_$(4+5)_$(PI) ${one}-${two}-${three}'")
+        self.assertEqual(expanded, "'xx_$(4+5)_$(PI) ${one}-${two}-${three}'")
+
     def test_get_thermo(self):
         self.lmp.command("units lj")
         self.lmp.command("atom_style atomic")