diff --git a/src/test/java/com/aliyun/tea/TeaModelTest.java b/src/test/java/com/aliyun/tea/TeaModelTest.java
index 85d7138..3480570 100644
--- a/src/test/java/com/aliyun/tea/TeaModelTest.java
+++ b/src/test/java/com/aliyun/tea/TeaModelTest.java
@@ -801,5 +801,17 @@ public void confirmTypeTest() {
         object6 = TeaModel.confirmType(String.class, list);
         Assert.assertEquals("[\"1\",2,true,{\"sub\":\"sub\"}]", object6);
 
+        Assert.assertNull(TeaModel.parseObject(null));
+        try {
+            TeaModel.confirmType(Float.class, "not-a-float");
+            Assert.fail();
+        } catch (NumberFormatException ignored) {
+        }
+        try {
+            TeaModel.confirmType(Double.class, "not-a-double");
+            Assert.fail();
+        } catch (NumberFormatException ignored) {
+        }
+        Assert.assertEquals(1L, TeaModel.confirmType(Long.class, 1.5F));
     }
 }
diff --git a/src/test/java/com/aliyun/tea/TeaResponseTest.java b/src/test/java/com/aliyun/tea/TeaResponseTest.java
index 1b02954..5d4d88d 100644
--- a/src/test/java/com/aliyun/tea/TeaResponseTest.java
+++ b/src/test/java/com/aliyun/tea/TeaResponseTest.java
@@ -25,4 +25,21 @@ public void getResponseBodyTest() throws Exception{
         response.body = new ByteArrayInputStream("test".getBytes("UTF-8"));
         Assert.assertEquals("test", response.getResponseBody());
     }
+
+    @Test
+    public void getResponseBodyExceptionTest() {
+        TeaResponse response = new TeaResponse();
+        response.body = new InputStream() {
+            @Override
+            public int read() throws java.io.IOException {
+                throw new java.io.IOException("read failed");
+            }
+        };
+        try {
+            response.getResponseBody();
+            Assert.fail();
+        } catch (TeaException e) {
+            Assert.assertEquals("read failed", e.getMessage());
+        }
+    }
 }
diff --git a/src/test/java/com/aliyun/tea/TeaTest.java b/src/test/java/com/aliyun/tea/TeaTest.java
index 2269836..26112e1 100644
--- a/src/test/java/com/aliyun/tea/TeaTest.java
+++ b/src/test/java/com/aliyun/tea/TeaTest.java
@@ -287,4 +287,44 @@ public void toReadableTest() throws IOException {
         String result = new String(bytes, 0, index);
         Assert.assertTrue(str.equals(result));
     }
+
+    @Test
+    public void doActionWithNullChainTest() {
+        ClientHelper.clients.clear();
+        TeaRequest request = new TeaRequest();
+        Map<String, String> map = new HashMap<>();
+        map.put("host", "www.google.com.hk");
+        request.protocol = "http";
+        request.headers = map;
+        request.method = "GET";
+        Map<String, Object> runtimeOptions = new HashMap<>();
+        runtimeOptions.put("readTimeout", "50000");
+        runtimeOptions.put("connectTimeout", "50000");
+        TeaResponse response = Tea.doAction(request, runtimeOptions, null);
+        Assert.assertEquals(200, response.statusCode);
+    }
+
+    @Test
+    public void toWriteableTest() {
+        Assert.assertNotNull(Tea.toWriteable(16));
+        try {
+            Tea.toWriteable(-1);
+            Assert.fail();
+        } catch (TeaException e) {
+            Assert.assertNotNull(e.getMessage());
+        }
+    }
+
+    @Test
+    public void sleepInterruptedTest() {
+        Thread.currentThread().interrupt();
+        try {
+            Tea.sleep(1000);
+            Assert.fail();
+        } catch (TeaException e) {
+            Assert.assertNotNull(e.getMessage());
+        } finally {
+            Thread.interrupted();
+        }
+    }
 }
diff --git a/src/test/java/com/aliyun/tea/logging/LoggerTest.java b/src/test/java/com/aliyun/tea/logging/LoggerTest.java
index bcfb55d..7804ac6 100644
--- a/src/test/java/com/aliyun/tea/logging/LoggerTest.java
+++ b/src/test/java/com/aliyun/tea/logging/LoggerTest.java
@@ -141,4 +141,41 @@ public void errorTest() {
         logger.error("test: {}, {}", "key1", "key2");
         logger.error("test: {}, {}, {}", "key1", "key2", "key3");
     }
+
+    @Test
+    public void defaultLoggerOverloadsTest() {
+        System.setProperty(DefaultLogger.SDK_LOG_LEVEL, "verbose");
+        DefaultLogger logger = new DefaultLogger("com.aliyun.tea.logging.NotExistClass");
+        Assert.assertEquals("com.aliyun.tea.logging.NotExistClass", logger.getName());
+
+        logger.trace("trace {}", "a");
+        logger.trace("trace", new RuntimeException("t"));
+        logger.debug("debug {}", "a");
+        logger.debug("debug {} {}", "a", "b");
+        logger.debug("debug", new RuntimeException("d"));
+        logger.info("info {}", "a");
+        logger.info("info {} {}", "a", "b");
+        logger.info("info", new RuntimeException("i"));
+        logger.warn("warn {}", "a");
+        logger.warn("warn {} {}", "a", "b");
+        logger.warn("warn", new RuntimeException("w"));
+        logger.error("error {}", "a");
+        logger.error("error {} {}", "a", "b");
+        logger.error("error", new RuntimeException("e"));
+    }
+
+    @Test
+    public void logLevelFromStringNullTest() {
+        Assert.assertEquals(LogLevel.NOT_SET, LogLevel.fromString(null));
+    }
+
+    @Test
+    public void clientLoggerThrowableInArgsTest() {
+        System.setProperty(DefaultLogger.SDK_LOG_LEVEL, "warn");
+        ClientLogger logger = new ClientLogger(LoggerTest.class);
+        logger.warning("warn with throwable: {}", "x", new RuntimeException("warn-ex"));
+        logger.error("error with throwable: {}", "y", new RuntimeException("error-ex"));
+        logger.verbose("empty-args");
+        logger.verbose("format-only", new Object[0]);
+    }
 }
diff --git a/src/test/java/com/aliyun/tea/okhttp/ClientHelperTest.java b/src/test/java/com/aliyun/tea/okhttp/ClientHelperTest.java
index 85e981b..cc29cc4 100644
--- a/src/test/java/com/aliyun/tea/okhttp/ClientHelperTest.java
+++ b/src/test/java/com/aliyun/tea/okhttp/ClientHelperTest.java
@@ -55,6 +55,11 @@ public void getClientKeyTest() throws NoSuchMethodException, InvocationTargetExc
         map.put("callTimeout", null);
         str = (String) getClientKey.invoke(ClientHelper.class, "0:0:0:0:0:0:0:1", 0, map);
         Assert.assertEquals("0:0:0:0:0:0:0:1:0:http://127.0.0.1:80:https://127.0.0.1:80:socks5://user:password@127.0.0.1:1080:1000:2000:false", str);
+
+        map.put("keepAliveDuration", 10000);
+        map.put("maxIdleConns", 5);
+        str = (String) getClientKey.invoke(ClientHelper.class, "0:0:0:0:0:0:0:1", 0, map);
+        Assert.assertEquals("0:0:0:0:0:0:0:1:0:http://127.0.0.1:80:https://127.0.0.1:80:socks5://user:password@127.0.0.1:1080:1000:2000:10000:5:false", str);
     }
 
     @Test
diff --git a/src/test/java/com/aliyun/tea/okhttp/OkHttpClientBuilderTest.java b/src/test/java/com/aliyun/tea/okhttp/OkHttpClientBuilderTest.java
index f25afb7..2e6cc3c 100644
--- a/src/test/java/com/aliyun/tea/okhttp/OkHttpClientBuilderTest.java
+++ b/src/test/java/com/aliyun/tea/okhttp/OkHttpClientBuilderTest.java
@@ -4,17 +4,113 @@
 import com.aliyun.tea.utils.DefaultHostnameVerifier;
 import okhttp3.OkHttpClient;
 import okhttp3.Protocol;
+import okhttp3.Request;
+import okhttp3.Response;
+import okhttp3.Route;
 import org.junit.Assert;
 import org.junit.Test;
 import org.mockito.Mockito;
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Stream;
 
 public class OkHttpClientBuilderTest {
     private Map<String, Object> map = new HashMap<>();
 
+    /**
+     * Build an ephemeral self-signed CA PEM at runtime (CN under *.local / UnitTestFixture).
+     * No production certificates or private keys are committed to the repository.
+     */
+    private static String createEphemeralSelfSignedCaPem(String commonName) throws Exception {
+        Path workDir = Files.createTempDirectory("tea-java-test-ca-");
+        Path keystore = workDir.resolve("test-ca.p12");
+        Path pemFile = workDir.resolve("test-ca.pem");
+        try {
+            Path keytool = resolveKeytool();
+            runKeytool(keytool,
+                    "-genkeypair",
+                    "-alias", "testca",
+                    "-keyalg", "RSA",
+                    "-keysize", "2048",
+                    "-validity", "1",
+                    "-dname", "CN=" + commonName + ",OU=UnitTestFixture,O=AliyunTeaJavaTest,C=CN",
+                    "-keystore", keystore.toString(),
+                    "-storetype", "PKCS12",
+                    "-storepass", "changeit",
+                    "-keypass", "changeit",
+                    "-noprompt");
+            runKeytool(keytool,
+                    "-exportcert",
+                    "-alias", "testca",
+                    "-keystore", keystore.toString(),
+                    "-storetype", "PKCS12",
+                    "-storepass", "changeit",
+                    "-rfc",
+                    "-file", pemFile.toString());
+            byte[] pemBytes = Files.readAllBytes(pemFile);
+            return new String(pemBytes, StandardCharsets.US_ASCII);
+        } finally {
+            deleteRecursively(workDir);
+        }
+    }
+
+    private static Path resolveKeytool() {
+        Path keytool = java.nio.file.Paths.get(System.getProperty("java.home"), "bin", "keytool");
+        if (!Files.isExecutable(keytool)) {
+            keytool = java.nio.file.Paths.get(System.getProperty("java.home"), "bin", "keytool.exe");
+        }
+        Assert.assertTrue("keytool not found under java.home", Files.isExecutable(keytool));
+        return keytool;
+    }
+
+    private static void runKeytool(Path keytool, String... args) throws Exception {
+        String[] command = new String[args.length + 1];
+        command[0] = keytool.toString();
+        System.arraycopy(args, 0, command, 1, args.length);
+        Process process = new ProcessBuilder(command)
+                .redirectErrorStream(true)
+                .start();
+        ByteArrayOutputStream output = new ByteArrayOutputStream();
+        try (InputStream in = process.getInputStream()) {
+            byte[] buf = new byte[1024];
+            int n;
+            while ((n = in.read(buf)) >= 0) {
+                output.write(buf, 0, n);
+            }
+        }
+        if (!process.waitFor(60, TimeUnit.SECONDS)) {
+            process.destroyForcibly();
+            Assert.fail("keytool timed out");
+        }
+        if (process.exitValue() != 0) {
+            Assert.fail("keytool failed: " + new String(output.toByteArray(), StandardCharsets.UTF_8));
+        }
+    }
+
+    private static void deleteRecursively(Path root) throws IOException {
+        if (!Files.exists(root)) {
+            return;
+        }
+        try (Stream<Path> walk = Files.walk(root)) {
+            walk.sorted(Comparator.reverseOrder()).forEach(path -> {
+                try {
+                    Files.deleteIfExists(path);
+                } catch (IOException ignored) {
+                    // best-effort cleanup of ephemeral fixtures
+                }
+            });
+        }
+    }
+
     @Test
     public void timeOutTest() {
         map.clear();
@@ -120,7 +216,7 @@ public void connectionPoolTest() {
     }
 
     @Test
-    public void certificateTest() throws IOException {
+    public void certificateTest() throws Exception {
         map.clear();
         OkHttpClientBuilder clientBuilder = Mockito.spy(new OkHttpClientBuilder());
         clientBuilder.certificate(map);
@@ -176,6 +272,71 @@ public void certificateTest() throws IOException {
         } catch (Exception e) {
             Assert.assertTrue(e instanceof TeaException);
         }
+
+        // ephemeral self-signed fixtures only — covers split + trust store without committed PEMs / CI CA secret
+        map.clear();
+        map.put("ignoreSSL", false);
+        String singleCa = createEphemeralSelfSignedCaPem("tea-java-unit-test.local");
+        map.put("ca", singleCa);
+        OkHttpClient clientWithCa = new OkHttpClientBuilder().certificate(map).buildOkHttpClient();
+        Assert.assertNotNull(clientWithCa.sslSocketFactory());
+
+        String dualCa = createEphemeralSelfSignedCaPem("tea-java-unit-test-a.local")
+                + "\n"
+                + createEphemeralSelfSignedCaPem("tea-java-unit-test-b.local");
+        map.put("ca", dualCa);
+        Assert.assertNotNull(new OkHttpClientBuilder().certificate(map).buildOkHttpClient().sslSocketFactory());
+
+        // non-PEM CA still enters splitPemCertificates else-branch
+        map.put("ca", "not-a-pem-certificate");
+        try {
+            new OkHttpClientBuilder().certificate(map);
+            Assert.fail();
+        } catch (TeaException e) {
+            Assert.assertNotNull(e.getMessage());
+        }
+    }
+
+    @Test
+    public void proxyAuthenticatorTest() throws Exception {
+        map.clear();
+        OkHttpClientBuilder clientBuilder = new OkHttpClientBuilder();
+        map.put("httpsProxy", "https://user:password@127.0.0.1:8080");
+        OkHttpClient client = clientBuilder.proxy(map).proxyAuthenticator(map).buildOkHttpClient();
+        Assert.assertNotNull(client.proxyAuthenticator());
+
+        Request request = new Request.Builder().url("http://example.com").build();
+        Response response = new Response.Builder()
+                .request(request)
+                .protocol(Protocol.HTTP_1_1)
+                .code(407)
+                .message("Proxy Authentication Required")
+                .build();
+        Request authenticated = client.proxyAuthenticator().authenticate((Route) null, response);
+        Assert.assertNotNull(authenticated);
+        Assert.assertNotNull(authenticated.header("Proxy-Authorization"));
+
+        map.clear();
+        map.put("socks5Proxy", "socks5://user:password@127.0.0.1:1080");
+        Assert.assertNotNull(new OkHttpClientBuilder().proxy(map).proxyAuthenticator(map).buildOkHttpClient());
+
+        map.clear();
+        map.put("httpProxy", "://bad-url");
+        try {
+            new OkHttpClientBuilder().proxy(map);
+            Assert.fail();
+        } catch (TeaException e) {
+            Assert.assertNotNull(e.getMessage());
+        }
+
+        map.clear();
+        map.put("httpProxy", "://bad-url");
+        try {
+            new OkHttpClientBuilder().proxyAuthenticator(map);
+            Assert.fail();
+        } catch (TeaException e) {
+            Assert.assertNotNull(e.getMessage());
+        }
     }
 
     @Test
diff --git a/src/test/java/com/aliyun/tea/okhttp/OkRequestBodyTest.java b/src/test/java/com/aliyun/tea/okhttp/OkRequestBodyTest.java
index ff15e09..7d350e3 100644
--- a/src/test/java/com/aliyun/tea/okhttp/OkRequestBodyTest.java
+++ b/src/test/java/com/aliyun/tea/okhttp/OkRequestBodyTest.java
@@ -44,5 +44,14 @@ public void writeToTest() throws IOException {
         Mockito.verify(body).writeTo(sink);
     }
 
+    @Test
+    public void contentLengthTest() throws IOException {
+        TeaRequest request = new TeaRequest();
+        OkRequestBody body = new OkRequestBody(request);
+        Assert.assertEquals(-1L, body.contentLength());
 
+        request.body = new ByteArrayInputStream("tes".getBytes("UTF-8"));
+        body = new OkRequestBody(request);
+        Assert.assertEquals(3L, body.contentLength());
+    }
 }
diff --git a/src/test/java/com/aliyun/tea/utils/IOUtilsTest.java b/src/test/java/com/aliyun/tea/utils/IOUtilsTest.java
index d51ca94..ba24cb3 100644
--- a/src/test/java/com/aliyun/tea/utils/IOUtilsTest.java
+++ b/src/test/java/com/aliyun/tea/utils/IOUtilsTest.java
@@ -13,6 +13,13 @@ public void closeQuietlyTest() {
         InputStream inputStream = new ByteArrayInputStream(source);
         try {
             IOUtils.closeQuietly(inputStream);
+            IOUtils.closeQuietly(null);
+            IOUtils.closeQuietly(new AutoCloseable() {
+                @Override
+                public void close() throws Exception {
+                    throw new IOException("close failed");
+                }
+            });
         } catch (Exception e) {
             Assert.fail();
         }
@@ -22,6 +29,7 @@ public void closeQuietlyTest() {
     public void closeIfCloseableTest() {
         try {
             IOUtils.closeIfCloseable("test");
+            IOUtils.closeIfCloseable(new ByteArrayInputStream(new byte[]{1}));
         } catch (Exception e) {
             Assert.fail();
         }
diff --git a/src/test/java/com/aliyun/tea/utils/TrueHostnameVerifierTest.java b/src/test/java/com/aliyun/tea/utils/TrueHostnameVerifierTest.java
index 0718daa..1b5c094 100644
--- a/src/test/java/com/aliyun/tea/utils/TrueHostnameVerifierTest.java
+++ b/src/test/java/com/aliyun/tea/utils/TrueHostnameVerifierTest.java
@@ -16,6 +16,9 @@ public void trueHostnameVerifierTest() throws InvocationTargetException, Instant
         Assert.assertTrue(trueHostnameVerifier.verify("authType", sslSession));
         Assert.assertTrue(trueHostnameVerifier.verify(null, null));
 
+        HostnameVerifier defaultVerifier = DefaultHostnameVerifier.getInstance(false);
+        Assert.assertFalse(defaultVerifier instanceof DefaultHostnameVerifier);
+
         Constructor<DefaultHostnameVerifier> constructor = DefaultHostnameVerifier.class.getDeclaredConstructor(boolean.class);
         constructor.setAccessible(true);
         DefaultHostnameVerifier hostnameVerifier = constructor.newInstance(false);
diff --git a/src/test/java/com/aliyun/tea/utils/ValidateTest.java b/src/test/java/com/aliyun/tea/utils/ValidateTest.java
index 80dfa05..ef532c5 100644
--- a/src/test/java/com/aliyun/tea/utils/ValidateTest.java
+++ b/src/test/java/com/aliyun/tea/utils/ValidateTest.java
@@ -6,6 +6,7 @@
 public class ValidateTest {
     @Test
     public void isTrueTest() {
+        Validate.isTrue(true, "message: %s", "test");
         try {
             Validate.isTrue(false, "message: %s", "test");
         } catch (Exception e) {
@@ -27,6 +28,7 @@ public void notNullTest() {
 
     @Test
     public void isNullTest() {
+        Validate.isNull(null, "message: %s", "test");
         try {
             Validate.isNull("not null", "message: %s", "test");
         } catch (Exception e) {