diff --git a/ContentGrabbingJi-framework-api/src/main/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessage.java b/ContentGrabbingJi-framework-api/src/main/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessage.java
index 8c770b7..94242c5 100644
--- a/ContentGrabbingJi-framework-api/src/main/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessage.java
+++ b/ContentGrabbingJi-framework-api/src/main/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessage.java
@@ -17,18 +17,28 @@
 
 package net.lamgc.cgj.bot.framework.message;
 
+import java.util.Objects;
+
 /**
  * 字符序列消息对象.
- * <p> 仅包含了一段字符串.
+ * <p> 仅包含了一段字符序列形式的内容.
  * @author LamGC
  */
 public final class CharSequenceMessage implements Message {
 
     private final CharSequence content;
 
+    /**
+     * 构造一个 CharSequenceMessage.
+     * @param content 字符序列形式的内容.
+     * @throws NullPointerException 当 content 为 {@code null},
+     *      或 content 为 {@link Message} 且 {@link Message#contentToString()} 返回 {@code null} 时抛出.
+     */
     public CharSequenceMessage(CharSequence content) {
+        Objects.requireNonNull(content);
+
         if (content instanceof Message) {
-            this.content = ((Message) content).contentToString();
+            this.content = Objects.requireNonNull(((Message) content).contentToString());
         } else {
             this.content = content;
         }
diff --git a/ContentGrabbingJi-framework-api/src/test/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessageTest.java b/ContentGrabbingJi-framework-api/src/test/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessageTest.java
new file mode 100644
index 0000000..682bd67
--- /dev/null
+++ b/ContentGrabbingJi-framework-api/src/test/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessageTest.java
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2020  LamGC
+ *
+ * ContentGrabbingJi is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * ContentGrabbingJi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.lamgc.cgj.bot.framework.message;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+
+/**
+ * @see CharSequenceMessage
+ */
+public class CharSequenceMessageTest {
+
+    @Test
+    public void buildTest() {
+        final String contentStr = "test";
+
+        Assert.assertEquals(contentStr, new CharSequenceMessage(contentStr).contentToString());
+        Assert.assertEquals(contentStr, new CharSequenceMessage(new StringBuilder(contentStr)).contentToString());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void nullContentTest() {
+        new CharSequenceMessage(null);
+    }
+
+    @Test
+    public void buildWithMessageTest() throws NoSuchFieldException, IllegalAccessException {
+        final String testContent = "test123";
+
+        class TestMessage implements Message {
+            @Override
+            public String contentToString() {
+                return testContent;
+            }
+        }
+
+        CharSequenceMessage charSequenceMessage = new CharSequenceMessage(new TestMessage());
+        Assert.assertEquals(testContent, charSequenceMessage.contentToString());
+
+        Field contentField = CharSequenceMessage.class.getDeclaredField("content");
+        contentField.setAccessible(true);
+        Assert.assertFalse(contentField.get(charSequenceMessage) instanceof Message);
+    }
+
+    @Test
+    public void toStringTest() {
+        final String testContent = "test";
+
+        Assert.assertEquals("CharSequenceMessage{content='" + testContent + "'}",
+                new CharSequenceMessage(testContent).toString());
+    }
+
+}
\ No newline at end of file