diff --git a/src/main/java/com/uber/cadence/internal/replay/SignalExternalWorkflowParameters.java b/src/main/java/com/uber/cadence/internal/replay/SignalExternalWorkflowParameters.java
index f5eb0a1b3..702d434b4 100644
--- a/src/main/java/com/uber/cadence/internal/replay/SignalExternalWorkflowParameters.java
+++ b/src/main/java/com/uber/cadence/internal/replay/SignalExternalWorkflowParameters.java
@@ -94,10 +94,20 @@ public SignalExternalWorkflowParameters withWorkflowId(String workflowId) {
 
   @Override
   public String toString() {
+
+    String inputStr;
+    if (input == null) {
+      inputStr = "";
+    } else if (input.length > 512) {
+      inputStr = new String(input, 0, 512, StandardCharsets.UTF_8);
+    } else {
+      inputStr = new String(input, StandardCharsets.UTF_8);
+    }
+
     StringBuilder sb = new StringBuilder();
     sb.append("{");
     sb.append("SignalName: " + signalName + ", ");
-    sb.append("Input: " + new String(input, 0, 512, StandardCharsets.UTF_8) + ", ");
+    sb.append("Input: " + inputStr + ", ");
     sb.append("WorkflowId: " + workflowId + ", ");
     sb.append("RunId: " + runId + ", ");
     sb.append("}");
@@ -108,6 +118,7 @@ public SignalExternalWorkflowParameters copy() {
     SignalExternalWorkflowParameters result = new SignalExternalWorkflowParameters();
     result.setInput(input);
     result.setRunId(runId);
+    result.setDomain(domain);
     result.setSignalName(signalName);
     result.setWorkflowId(workflowId);
     return result;
diff --git a/src/test/java/com/uber/cadence/internal/replay/SignalExternalWorkflowParametersTest.java b/src/test/java/com/uber/cadence/internal/replay/SignalExternalWorkflowParametersTest.java
new file mode 100644
index 000000000..6e5357510
--- /dev/null
+++ b/src/test/java/com/uber/cadence/internal/replay/SignalExternalWorkflowParametersTest.java
@@ -0,0 +1,190 @@
+/**
+ * Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * <p>Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ * <p>Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file
+ * except in compliance with the License. A copy of the License is located at
+ *
+ * <p>http://aws.amazon.com/apache2.0
+ *
+ * <p>or in the "license" file accompanying this file. This file 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 com.uber.cadence.internal.replay;
+
+import static org.junit.Assert.*;
+
+import java.lang.reflect.Field;
+import java.nio.charset.StandardCharsets;
+import org.junit.Test;
+
+public class SignalExternalWorkflowParametersTest {
+
+  @Test
+  public void testSetAndGetDomain() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+    params.setDomain("TestDomain");
+    assertEquals("TestDomain", params.getDomain());
+  }
+
+  @Test
+  public void testSetAndGetInput() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+    byte[] input = "TestInput".getBytes(StandardCharsets.UTF_8);
+    params.setInput(input);
+    assertArrayEquals(input, params.getInput());
+  }
+
+  @Test
+  public void testWithInputChain() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+
+    byte[] input = "ChainInput".getBytes(StandardCharsets.UTF_8);
+    SignalExternalWorkflowParameters result = params.withInput(input);
+    assertArrayEquals(input, params.getInput());
+    assertSame(params, result);
+  }
+
+  @Test
+  public void testSetAndGetRunId() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+    params.setRunId("TestRunId");
+    assertEquals("TestRunId", params.getRunId());
+  }
+
+  @Test
+  public void testWithRunIdChain() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+
+    SignalExternalWorkflowParameters result = params.withRunId("ChainRunId");
+    assertEquals("ChainRunId", params.getRunId());
+    assertSame(params, result);
+  }
+
+  @Test
+  public void testSetAndGetSignalName() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+
+    params.setSignalName("TestSignalName");
+    assertEquals("TestSignalName", params.getSignalName());
+  }
+
+  @Test
+  public void testWithSignalNameChain() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+    SignalExternalWorkflowParameters result = params.withSignalName("ChainSignalName");
+    assertEquals("ChainSignalName", params.getSignalName());
+    assertSame(params, result);
+  }
+
+  @Test
+  public void testSetAndGetWorkflowId() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+    params.setWorkflowId("TestWorkflowId");
+    assertEquals("TestWorkflowId", params.getWorkflowId());
+  }
+
+  @Test
+  public void testWithWorkflowIdChain() {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+    SignalExternalWorkflowParameters result = params.withWorkflowId("ChainWorkflowId");
+    assertEquals("ChainWorkflowId", params.getWorkflowId());
+    assertSame(params, result);
+  }
+
+  @Test
+  public void testStringification() {
+
+    String longStr =
+        "1000000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000000"
+            + "0000000000000000000000000000000000000000000000000000000000000000000000001";
+
+    SignalExternalWorkflowParameters longParams =
+        new SignalExternalWorkflowParameters()
+            .withWorkflowId("ChainWorkflowId")
+            .withSignalName("signalName")
+            .withInput(longStr.getBytes())
+            .withRunId("some-run-id");
+
+    SignalExternalWorkflowParameters shortParams =
+        new SignalExternalWorkflowParameters()
+            .withWorkflowId("ChainWorkflowId")
+            .withSignalName("signalName")
+            .withInput("smol".getBytes())
+            .withRunId("some-run-id");
+
+    assertEquals(
+        "{SignalName: signalName, Input: "
+            + longStr.substring(0, 512)
+            + ", WorkflowId: ChainWorkflowId, RunId: some-run-id, }",
+        longParams.toString());
+
+    assertEquals(
+        "{SignalName: signalName, Input: "
+            + "smol"
+            + ", WorkflowId: ChainWorkflowId, RunId: some-run-id, }",
+        shortParams.toString());
+
+    assertEquals(
+        "{SignalName: null, Input: , WorkflowId: null, RunId: null, }",
+        new SignalExternalWorkflowParameters().toString());
+  }
+
+  @Test
+  public void testClone() throws CloneNotSupportedException {
+    SignalExternalWorkflowParameters params = new SignalExternalWorkflowParameters();
+    params.setDomain("Domain");
+    params.setRunId("RunId");
+    params.setSignalName("SignalName");
+    params.setWorkflowId("WorkflowId");
+    params.setInput("Input".getBytes(StandardCharsets.UTF_8));
+
+    SignalExternalWorkflowParameters clonedParams = params.copy();
+
+    assertNotSame(params, clonedParams);
+
+    assertEquals(params.getDomain(), clonedParams.getDomain());
+    assertArrayEquals(params.getInput(), clonedParams.getInput());
+    assertEquals(params.getRunId(), clonedParams.getRunId());
+    assertEquals(params.getSignalName(), clonedParams.getSignalName());
+    assertEquals(params.getWorkflowId(), clonedParams.getWorkflowId());
+
+    // there's 5 assertions here
+    // update if there's any additional properties
+    assertEquals(5, getPropertyCount(params));
+  }
+
+  private static int getPropertyCount(Object obj) {
+    int count = 0;
+    Class<?> clazz = obj.getClass();
+
+    while (clazz != null) {
+      Field[] fields = clazz.getDeclaredFields();
+
+      for (Field field : fields) {
+        if (!field.getName().equals("$jacocoData")) {
+          count++;
+        }
+      }
+      clazz = clazz.getSuperclass();
+    }
+
+    return count;
+  }
+}