diff --git a/core/fxcrt/bytestring_unittest.cpp b/core/fxcrt/bytestring_unittest.cpp
index fe01957..a726b66 100644
--- a/core/fxcrt/bytestring_unittest.cpp
+++ b/core/fxcrt/bytestring_unittest.cpp
@@ -112,6 +112,26 @@
     }
     EXPECT_EQ(1, string1.ReferenceCountForTesting());
   }
+  {
+    // From char*.
+    ByteString string1 = "abc";
+    EXPECT_EQ("abc", string1);
+    string1 = nullptr;
+    EXPECT_TRUE(string1.IsEmpty());
+    string1 = "def";
+    EXPECT_EQ("def", string1);
+    string1 = "";
+    EXPECT_TRUE(string1.IsEmpty());
+  }
+  {
+    // From ByteStringView.
+    ByteString string1(ByteStringView("abc"));
+    EXPECT_EQ("abc", string1);
+    string1 = ByteStringView("");
+    EXPECT_TRUE(string1.IsEmpty());
+    string1 = ByteStringView("def");
+    EXPECT_EQ("def", string1);
+  }
 }
 
 TEST(ByteString, OperatorLT) {
diff --git a/core/fxcrt/widestring_unittest.cpp b/core/fxcrt/widestring_unittest.cpp
index 7114ae4..02c25c1 100644
--- a/core/fxcrt/widestring_unittest.cpp
+++ b/core/fxcrt/widestring_unittest.cpp
@@ -109,6 +109,26 @@
     }
     EXPECT_EQ(1, string1.ReferenceCountForTesting());
   }
+  {
+    // From wchar_t*.
+    WideString string1 = L"abc";
+    EXPECT_EQ(L"abc", string1);
+    string1 = nullptr;
+    EXPECT_TRUE(string1.IsEmpty());
+    string1 = L"def";
+    EXPECT_EQ(L"def", string1);
+    string1 = L"";
+    EXPECT_TRUE(string1.IsEmpty());
+  }
+  {
+    // From WideStringView.
+    WideString string1(WideStringView(L"abc"));
+    EXPECT_EQ(L"abc", string1);
+    string1 = WideStringView(L"");
+    EXPECT_TRUE(string1.IsEmpty());
+    string1 = WideStringView(L"def");
+    EXPECT_EQ(L"def", string1);
+  }
 }
 
 TEST(WideString, OperatorLT) {