diff --git a/tests/unit-initcpio.cpp b/tests/unit-initcpio.cpp
index f5e994d..af12389 100644
--- a/tests/unit-initcpio.cpp
+++ b/tests/unit-initcpio.cpp
@@ -57,12 +57,20 @@ int main() {
     // Insert data.
     initcpio.append_module("radeon");
     initcpio.append_hook("btrfs");
-    initcpio.modules.insert(initcpio.modules.end(), {"crc32c-intel"});
+    initcpio.append_module("crc32c-intel");
     initcpio.hooks.insert(initcpio.hooks.end(), {"usr", "lvm2", "zfs"});
 
     // Write data.
     assert(initcpio.write());
 
+    // Checking insertion of equal items
+    initcpio.append_module("radeon");
+    initcpio.append_hook("btrfs");
+    initcpio.append_module("crc32c-intel");
+
+    // Write data.
+    assert(initcpio.write());
+
     // Check if file is equal to test data.
     // "\n# MODULES\nMODULES=(crc32c-intel)\n\n# BINARIES\nBINARIES=()\n\n# FILES\nFILES=()\n\n# HOOKS\nHOOKS=(base usr lvm2 zfs)"\n
     const auto& file_content = utils::read_whole_file(filename);