diff --git a/owner-extras/src/test/java/org/aeonbits/owner/extras/loaders/HoconReaderTest.java b/owner-extras/src/test/java/org/aeonbits/owner/extras/loaders/HoconReaderTest.java
new file mode 100644
index 00000000..0b415c2d
--- /dev/null
+++ b/owner-extras/src/test/java/org/aeonbits/owner/extras/loaders/HoconReaderTest.java
@@ -0,0 +1,149 @@
+/*
+ * Copyright (c) 2012-2026, Luigi R. Viggiano, Matteo Baccan
+ * All rights reserved.
+ *
+ * This software is distributable under the BSD license.
+ * See the terms of the BSD license in the documentation provided with this software.
+ */
+package org.aeonbits.owner.extras.loaders;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.lang.reflect.Constructor;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.Properties;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+/**
+ * Direct unit tests for {@link HoconReader}.
+ *
+ * @author Matteo Baccan
+ */
+public class HoconReaderTest {
+
+    @Rule
+    public final TemporaryFolder folder = new TemporaryFolder();
+
+    private int documents;
+
+    @Test
+    public void privateConstructorCanBeInstantiatedForCoverage() throws Exception {
+        Constructor<HoconReader> constructor = HoconReader.class.getDeclaredConstructor();
+        constructor.setAccessible(true);
+        HoconReader instance = constructor.newInstance();
+        assertNotNull(instance);
+    }
+
+    @Test
+    public void readsObjectAndFlattensKeys() throws Exception {
+        Properties result = read("server { host = localhost\n port = 8080 }");
+        assertEquals("localhost", result.getProperty("server.host"));
+        assertEquals("8080", result.getProperty("server.port"));
+    }
+
+    @Test
+    public void readsIndexedListsAndNestedObjectLists() throws Exception {
+        Properties result = read("ports = [80, 443]\nservers = [ { host = alpha }, { host = beta } ]");
+        assertEquals("80", result.getProperty("ports[0]"));
+        assertEquals("443", result.getProperty("ports[1]"));
+        assertEquals("alpha", result.getProperty("servers[0].host"));
+        assertEquals("beta", result.getProperty("servers[1].host"));
+    }
+
+    @Test
+    public void handlesEmptyListAndNullValue() throws Exception {
+        Properties result = read("emptyList = []\nnullValue = null\nvalidKey = value");
+        assertEquals("", result.getProperty("emptyList"));
+        assertFalse(result.containsKey("nullValue"));
+        assertEquals("value", result.getProperty("validKey"));
+    }
+
+    @Test
+    public void resolvesSubstitutionsAndSelfReferences() throws Exception {
+        Properties result = read("base = /srv\npath = ${base}/app\nenvPath = /bin\nenvPath = ${envPath}\":/usr/bin\"");
+        assertEquals("/srv/app", result.getProperty("path"));
+        assertEquals("/bin:/usr/bin", result.getProperty("envPath"));
+    }
+
+    @Test
+    public void handlesOptionalSubstitutionAndSystemProperties() throws Exception {
+        String key = "owner.hocon.reader.test.prop";
+        System.setProperty(key, "sysVal");
+        com.typesafe.config.ConfigFactory.invalidateCaches();
+        try {
+            Properties result = read("missingOpt = ${?NON_EXISTENT_VAR}\nsysProp = ${" + key + "}");
+            assertFalse(result.containsKey("missingOpt"));
+            assertEquals("sysVal", result.getProperty("sysProp"));
+            assertNull(result.getProperty(key));
+        } finally {
+            System.clearProperty(key);
+        }
+    }
+
+    @Test
+    public void throwsIOExceptionForMissingSourceFile() {
+        File missingFile = new File(folder.getRoot(), "does-not-exist.conf");
+        Properties result = new Properties();
+        try {
+            HoconReader.read(result, missingFile.toURI());
+            fail("Expected IOException for non-existent file");
+        } catch (IOException expected) {
+            // expected
+        }
+    }
+
+    @Test
+    public void throwsUnsupportedOperationExceptionOnParseErrorAndHidesCredentials() throws Exception {
+        File file = writeDocument("invalid { hocon = [ ]");
+        URI uriWithCreds = new URI("file", "user:secretpassword", "localhost", -1, file.toURI().getPath(), null, null);
+
+        try {
+            Properties result = new Properties();
+            HoconReader.read(result, uriWithCreds);
+            fail("Expected UnsupportedOperationException for malformed document");
+        } catch (UnsupportedOperationException expected) {
+            assertTrue(expected.getMessage().contains("could not be read as HOCON"));
+            assertTrue(expected.getMessage().contains("***@localhost"));
+            assertFalse(expected.getMessage().contains("secretpassword"));
+        }
+    }
+
+    @Test
+    public void throwsUnsupportedOperationExceptionForMissingRequiredSubstitution() throws Exception {
+        try {
+            read("host = ${no.such.required.property.anywhere}");
+            fail("Expected UnsupportedOperationException for unresolved required substitution");
+        } catch (UnsupportedOperationException expected) {
+            assertTrue(expected.getMessage().contains("could not be read as HOCON"));
+        }
+    }
+
+    private Properties read(String content) throws IOException {
+        File file = writeDocument(content);
+        Properties result = new Properties();
+        HoconReader.read(result, file.toURI());
+        return result;
+    }
+
+    private File writeDocument(String content) throws IOException {
+        File file = folder.newFile("test" + documents++ + ".conf");
+        try (Writer out = new OutputStreamWriter(Files.newOutputStream(file.toPath()), StandardCharsets.UTF_8)) {
+            out.write(content);
+        }
+        return file;
+    }
+}