diff --git a/core/base/test/TStringTest.cxx b/core/base/test/TStringTest.cxx
index 8ed2c22720206..9ae5849c38653 100644
--- a/core/base/test/TStringTest.cxx
+++ b/core/base/test/TStringTest.cxx
@@ -1,8 +1,8 @@
 #include "gtest/gtest.h"
-
 #include "ROOT/TestSupport.hxx"
-
 #include "TString.h"
+#include "TObjArray.h"
+#include "TObjString.h"
 
 TEST(TString, Basics)
 {
@@ -10,8 +10,60 @@ TEST(TString, Basics)
    ROOT_EXPECT_ERROR(s = new TString("Test", -5), "TString::TString", "Negative length!");
    delete s;
    TString p("Test", 1);
-   EXPECT_STREQ("T", p);
+   EXPECT_STREQ("T", p.Data());
    TString a = "test";
    ROOT_EXPECT_ERROR(a.Append("s", -5), "TString::Replace", "Negative number of replacement characters!");
-   EXPECT_STREQ("test", a);
+   EXPECT_STREQ("test", a.Data());
+}
+
+TEST(TString, Contains)
+{
+   TString s("HelloWorld");
+   EXPECT_TRUE(s.Contains("World"));
+   EXPECT_TRUE(s.Contains("hello", TString::kIgnoreCase));
+   EXPECT_FALSE(s.Contains("hello", TString::kExact));
+}
+
+TEST(TString, ReplaceAll)
+{
+   TString s("The quick brown fox");
+   s.ReplaceAll("quick", "slow");
+   EXPECT_STREQ("The slow brown fox", s.Data());
+
+   s.ReplaceAll("fox", "dog");
+   EXPECT_STREQ("The slow brown dog", s.Data());
+}
+
+TEST(TString, CaseConversion)
+{
+   TString s("ROOT Framework");
+   s.ToUpper();
+   EXPECT_STREQ("ROOT FRAMEWORK", s.Data());
+   s.ToLower();
+   EXPECT_STREQ("root framework", s.Data());
+}
+
+TEST(TString, Formatting)
+{
+   TString s;
+   s.Form("Number %d and string %s", 42, "test");
+   EXPECT_STREQ("Number 42 and string test", s.Data());
 }
+
+TEST(TString, Substring)
+{
+   TString s("abcdef");
+   TString sub = s(1, 3);
+   EXPECT_STREQ("bcd", sub.Data());
+}
+
+TEST(TString, Tokenize)
+{
+   TString s("apple,banana,orange");
+   std::unique_ptr<TObjArray> tokens(s.Tokenize(","));
+   ASSERT_EQ(3, tokens->GetEntries());
+   EXPECT_STREQ("apple", ((TObjString*)tokens->At(0))->GetString().Data());
+   EXPECT_STREQ("banana", ((TObjString*)tokens->At(1))->GetString().Data());
+   EXPECT_STREQ("orange", ((TObjString*)tokens->At(2))->GetString().Data());
+}
+