diff --git a/src/test/java/org/tikv/common/apiversion/RequestKeyCodecTest.java b/src/test/java/org/tikv/common/apiversion/RequestKeyCodecTest.java
index 60ffa53e70..ed97fcdb81 100644
--- a/src/test/java/org/tikv/common/apiversion/RequestKeyCodecTest.java
+++ b/src/test/java/org/tikv/common/apiversion/RequestKeyCodecTest.java
@@ -178,27 +178,33 @@ public class RequestKeyCodecTest {
     assertEquals(ByteString.EMPTY, decoded.getEndKey());
 
     // test region out of keyspace
-    region =
-        Region.newBuilder()
-            .setStartKey(ByteString.EMPTY)
-            .setEndKey(CodecUtils.encode(v2.keyPrefix))
-            .build();
+    {
+      ByteString m_123 = CodecUtils.encode(ByteString.copyFromUtf8("m_123"));
+      ByteString m_124 = CodecUtils.encode(ByteString.copyFromUtf8("m_124"));
+      ByteString infiniteEndKey_0 =
+          CodecUtils.encode(v2.infiniteEndKey.concat(ByteString.copyFrom(new byte[] {0})));
+      ByteString t_123 = CodecUtils.encode(ByteString.copyFromUtf8("t_123"));
+      ByteString y_123 = CodecUtils.encode(ByteString.copyFromUtf8("y_123"));
 
-    try {
-      decoded = v2.decodeRegion(region);
-      fail();
-    } catch (Exception ignored) {
-    }
+      ByteString[][] outOfKeyspaceCases = {
+        {ByteString.EMPTY, CodecUtils.encode(v2.keyPrefix)}, // ["", "r000"/"x000")
+        {ByteString.EMPTY, m_123},
+        {m_123, m_124},
+        {m_124, CodecUtils.encode(v2.keyPrefix)},
+        {CodecUtils.encode(v2.infiniteEndKey), ByteString.EMPTY}, // ["r001"/"x001", "")
+        {CodecUtils.encode(v2.infiniteEndKey), infiniteEndKey_0},
+        {infiniteEndKey_0, t_123},
+        {y_123, ByteString.EMPTY}, // "y_123" is bigger than "infiniteEndKey" for both raw & txn.
+      };
 
-    region =
-        Region.newBuilder()
-            .setStartKey(CodecUtils.encode(v2.infiniteEndKey))
-            .setEndKey(ByteString.EMPTY)
-            .build();
-    try {
-      decoded = v2.decodeRegion(region);
-      fail();
-    } catch (Exception ignored) {
+      for (ByteString[] testCase : outOfKeyspaceCases) {
+        region = Region.newBuilder().setStartKey(testCase[0]).setEndKey(testCase[1]).build();
+        try {
+          decoded = v2.decodeRegion(region);
+          fail(String.format("[%s,%s): %s", testCase[0], testCase[1], decoded.toString()));
+        } catch (Exception ignored) {
+        }
+      }
     }
 
     // case: regionStartKey == "" < keyPrefix < regionEndKey < infiniteEndKey