Add tests for LongExtension methods

pgpainless-core/src/main/kotlin/openpgp/LongExtensions.kt

@@ -9,7 +9,7 @@ fun Long.openPgpKeyId(): String {
     return String.format("%016X", this).uppercase()
 }
 
-/** Parse a Long form a 16 digit hex encoded OpenPgp key-ID. */
+/** Parse a Long from a 16 digit hex encoded OpenPgp key-ID. */
 fun Long.Companion.fromOpenPgpKeyId(hexKeyId: String): Long {
     require("^[0-9A-Fa-f]{16}$".toRegex().matches(hexKeyId)) {
         "Provided long key-id does not match expected format. " +

pgpainless-core/src/main/kotlin/org/pgpainless/key/util/KeyIdUtil.kt

@@ -17,10 +17,7 @@ class KeyIdUtil {
          * @param longKeyId 16-digit hexadecimal string
          * @return key-id converted to [Long].
          */
-        @JvmStatic
+        @JvmStatic fun fromLongKeyId(longKeyId: String) = Long.fromOpenPgpKeyId(longKeyId)
-        @Deprecated(
-            "Superseded by Long extension method.", ReplaceWith("Long.fromHexKeyId(longKeyId)"))
-        fun fromLongKeyId(longKeyId: String) = Long.fromOpenPgpKeyId(longKeyId)
 
         /**
          * Format a long key-ID as upper-case hex string.

pgpainless-core/src/test/java/openpgp/LongExtensionTest.java

@@ -0,0 +1,38 @@
+// SPDX-FileCopyrightText: 2025 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package openpgp;
+
+import org.junit.jupiter.api.Test;
+import org.pgpainless.key.util.KeyIdUtil;
+
+import java.util.Random;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class LongExtensionTest {
+
+    private final Random random = new Random();
+
+    @Test
+    public void testFromOpenPGPKeyId() {
+        long id = random.nextLong();
+        String hexId = LongExtensionsKt.openPgpKeyId(id);
+        assertEquals(16, hexId.length());
+        // Calling companion object extension methods from java is tricky.
+        // KeyIdUtil delegates to Long.Companion extension method though.
+        long parsed = KeyIdUtil.fromLongKeyId(hexId);
+        assertEquals(id, parsed, "Long MUST still match after converting to hex and back.");
+    }
+
+    @Test
+    public void testParsingMalformedHexIdFails() {
+        assertThrows(IllegalArgumentException.class, () ->
+                        KeyIdUtil.fromLongKeyId("00"),
+                "Hex encoding is too short, expect 16 chars.");assertThrows(IllegalArgumentException.class, () ->
+                        KeyIdUtil.fromLongKeyId("00010203040506XX"),
+                "Hex encoding contains non-hex chars.");
+    }
+}