diff --git a/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java b/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java
index 3663a48..c9a991f 100644
--- a/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java
+++ b/src/main/java/de/stklcode/jvault/connector/HTTPVaultConnector.java
@@ -859,7 +859,7 @@ public class HTTPVaultConnector implements VaultConnector {
                     }
             }
         } catch (IOException e) {
-            throw new InvalidResponseException("Unable to read response", e);
+            throw new InvalidResponseException(Error.READ_RESPONSE, e);
         } finally {
             if (response != null && response.getEntity() != null)
                 try {
@@ -874,6 +874,7 @@ public class HTTPVaultConnector implements VaultConnector {
      * Inner class to bundle common error messages.
      */
     private static final class Error {
+        private static final String READ_RESPONSE = "Unable to read response";
         private static final String PARSE_RESPONSE = "Unable to parse response";
         private static final String UNEXPECTED_RESPONSE = "Received response where none was expected";
         private static final String URI_FORMAT = "Invalid URI format";
diff --git a/src/test/java/de/stklcode/jvault/connector/HTTPVaultConnectorOfflineTest.java b/src/test/java/de/stklcode/jvault/connector/HTTPVaultConnectorOfflineTest.java
new file mode 100644
index 0000000..3babf79
--- /dev/null
+++ b/src/test/java/de/stklcode/jvault/connector/HTTPVaultConnectorOfflineTest.java
@@ -0,0 +1,128 @@
+/*
+ * Copyright 2016-2017 Stefan Kalscheuer
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package de.stklcode.jvault.connector;
+
+import de.stklcode.jvault.connector.exception.InvalidRequestException;
+import de.stklcode.jvault.connector.exception.InvalidResponseException;
+import org.junit.Test;
+
+import javax.net.ssl.SSLContext;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.net.ServerSocket;
+import java.security.NoSuchAlgorithmException;
+
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertThat;
+
+/**
+ * JUnit test for HTTP Vault connector.
+ * This test suite contains tests that do not require connection to an actual Vault instance.
+ *
+ * @author Stefan Kalscheuer
+ * @since 0.7.0
+ */
+public class HTTPVaultConnectorOfflineTest {
+
+    /**
+     * Test constductors of the {@link HTTPVaultConnector} class.
+     */
+    @Test
+    public void constructorTest() throws NoSuchAlgorithmException {
+        final String url = "https://vault.example.net/test/";
+        final String hostname = "vault.example.com";
+        final Integer port = 1337;
+        final String prefix = "/custom/prefix/";
+        final Integer retries = 42;
+        final String expectedNoTls = "http://" + hostname + "/v1/";
+        final String expectedCustomPort = "https://" + hostname + ":" + port + "/v1/";
+        final String expectedCustomPrefix = "https://" + hostname + ":" + port + prefix;
+        final SSLContext sslContext = SSLContext.getInstance("TLS");
+
+        // Most basic constructor expects complete URL.
+        HTTPVaultConnector connector = new HTTPVaultConnector(url);
+        assertThat("Unexpected base URL", getPrivate(connector, "baseURL"), is(url));
+
+        // Now override TLS usage.
+        connector = new HTTPVaultConnector(hostname, false);
+        assertThat("Unexpected base URL with TLS disabled", getPrivate(connector, "baseURL"), is(expectedNoTls));
+
+        // Specify custom port.
+        connector = new HTTPVaultConnector(hostname, true, port);
+        assertThat("Unexpected base URL with custom port", getPrivate(connector, "baseURL"), is(expectedCustomPort));
+
+        // Specify custom prefix.
+        connector = new HTTPVaultConnector(hostname, true, port, prefix);
+        assertThat("Unexpected base URL with custom prefix", getPrivate(connector, "baseURL"), is(expectedCustomPrefix));
+        assertThat("SSL context set, but not specified", getPrivate(connector, "sslContext"), is(nullValue()));
+
+        // Provide custom SSL context.
+        connector = new HTTPVaultConnector(hostname, true, port, prefix, sslContext);
+        assertThat("Unexpected base URL with custom prefix", getPrivate(connector, "baseURL"), is(expectedCustomPrefix));
+        assertThat("SSL context not filled correctly", getPrivate(connector, "sslContext"), is(sslContext));
+
+        // Specify number of retries.
+        connector = new HTTPVaultConnector(url, sslContext, retries);
+        assertThat("Number of retries not set correctly", getPrivate(connector, "retries"), is(retries));
+    }
+
+    /**
+     * This test is designed to test exceptions caught and thrown by seal-methods if Vault is not reachable.
+     */
+    @Test
+    public void sealExceptionTest() throws IOException {
+        HTTPVaultConnector connector = new HTTPVaultConnector("foo:/\\1nv4l1d_UrL");
+        try {
+            connector.sealStatus();
+            fail("Querying seal status succeeded on invalid URL");
+        } catch (Exception e) {
+            assertThat("Unexpected type of exception", e, instanceOf(InvalidRequestException.class));
+            assertThat("Unexpected exception message", e.getMessage(), is("Invalid URI format"));
+        }
+
+        // Create socket on free port to ensure no other process is listening on the specified URL.
+        try (ServerSocket s = new ServerSocket(0)) {
+            connector = new HTTPVaultConnector("https://127.0.0.1:" + s.getLocalPort(), null, 0, 250);
+            try {
+                connector.sealStatus();
+                fail("Querying seal status succeeded on invalid instance");
+            } catch (Exception e) {
+                assertThat("Unexpected type of exception", e, instanceOf(InvalidResponseException.class));
+                assertThat("Unexpected exception message", e.getMessage(), is("Unable to read response"));
+            }
+        }
+    }
+
+    private void fail(String s) {
+    }
+
+    private Object getPrivate(Object target, String fieldName) {
+        try {
+            Field field = target.getClass().getDeclaredField(fieldName);
+            if (field.isAccessible())
+                return field.get(target);
+            field.setAccessible(true);
+            Object value = field.get(target);
+            field.setAccessible(false);
+            return value;
+        } catch (NoSuchFieldException | IllegalAccessException e) {
+            return null;
+        }
+    }
+}