Added tests for dns resolver

src/main/java/com/hivemq/security/ssl/DnsResolver.java

@@ -0,0 +1,32 @@
+package com.hivemq.security.ssl;
+
+import java.util.Map;
+
+public class DnsResolver {
+
+    private final Map<String, String> dnsMap;
+
+    DnsResolver(final Map<String, String> dnsMap) {
+        this.dnsMap = dnsMap;
+    }
+
+    String resolve(final String domain) {
+        String alias = dnsMap.get(domain);
+        if (alias != null) {
+            return alias;
+        }
+
+        int index = domain.indexOf('.');
+        while (index >= 0) {
+            final String wildcardDomain = "*" + domain.substring(index);
+            alias = dnsMap.get(wildcardDomain);
+            if (alias != null) {
+                return alias;
+            }
+            index = domain.indexOf('.', index + 1);
+        }
+
+        return null;
+    }
+
+}

src/main/java/com/hivemq/security/ssl/SslContextFactory.java

@@ -242,33 +242,4 @@ private static Set<String> getDnsHostnamesFromCertificate(final X509Certificate
         throw new SslException("Invalid auth mode: " + clientAuthMode);
     }
 
-    private static class DnsResolver {
-
-        private final Map<String, String> dnsMap;
-
-        DnsResolver(final Map<String, String> dnsMap) {
-            this.dnsMap = dnsMap;
-        }
-
-        String resolve(final String domain) {
-            String alias = dnsMap.get(domain);
-            if (alias != null) {
-                return alias;
-            }
-
-            int index = domain.indexOf('.');
-            while (index >= 0) {
-                final String wildcardDomain = "*" + domain.substring(index);
-                alias = dnsMap.get(wildcardDomain);
-                if (alias != null) {
-                    return alias;
-                }
-                index = domain.indexOf('.', index + 1);
-            }
-
-            return null;
-        }
-
-    }
-
 }

src/test/java/com/hivemq/security/ssl/DnsResolverTest.java

@@ -0,0 +1,51 @@
+package com.hivemq.security.ssl;
+
+import org.junit.Test;
+
+import java.util.Map;
+
+import static org.junit.Assert.*;
+
+public class DnsResolverTest {
+    public static final String ALIAS_1 = "alias1";
+    public static final String TEST_EXAMPLE_COM = "test.example.com";
+
+    @Test
+    public void test_resolve_simple_dns_name() {
+        final DnsResolver dnsResolver = new DnsResolver(Map.of(TEST_EXAMPLE_COM, ALIAS_1));
+
+        final String resolve = dnsResolver.resolve(TEST_EXAMPLE_COM);
+
+        assertNotNull(resolve);
+        assertEquals(ALIAS_1, resolve);
+    }
+
+    @Test
+    public void test_resolve_non_matching_dns_name() {
+        final DnsResolver dnsResolver = new DnsResolver(Map.of(TEST_EXAMPLE_COM, ALIAS_1));
+
+        final String resolve = dnsResolver.resolve("other.example.com");
+
+        assertNull(resolve);
+    }
+
+    @Test
+    public void test_resolve_wildcard_dns_name() {
+        final DnsResolver dnsResolver = new DnsResolver(Map.of("*.example.com", ALIAS_1));
+
+        final String resolve = dnsResolver.resolve(TEST_EXAMPLE_COM);
+
+        assertNotNull(resolve);
+        assertEquals(ALIAS_1, resolve);
+    }
+
+    @Test
+    public void test_resolve_nested_wildcard_dns_name() {
+        final DnsResolver dnsResolver = new DnsResolver(Map.of("*.example.com", ALIAS_1));
+
+        final String resolve = dnsResolver.resolve("sub.test.example.com");
+
+        assertNotNull(resolve);
+        assertEquals(ALIAS_1, resolve);
+    }
+}