diff --git a/test/testbufferoverrun.cpp b/test/testbufferoverrun.cpp
index 4069a164a..c655c3d8f 100644
--- a/test/testbufferoverrun.cpp
+++ b/test/testbufferoverrun.cpp
@@ -166,6 +166,7 @@ private:
         TEST_CASE(array_index_72); // #11784
         TEST_CASE(array_index_73); // #11530
         TEST_CASE(array_index_74); // #11088
+        TEST_CASE(array_index_75);
         TEST_CASE(array_index_multidim);
         TEST_CASE(array_index_switch_in_for);
         TEST_CASE(array_index_for_in_for);   // FP: #2634
@@ -1976,6 +1977,18 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    // #1644
+    void array_index_75()
+    {
+        check("void f() {\n"
+              "    char buf[10];\n"
+              "    int i = 10;\n"
+              "    while (i >= 3)\n"
+              "        buf[i--] = 0;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:5]: (error) Array 'buf[10]' accessed at index 10, which is out of bounds.\n", errout.str());
+    }
+
     void array_index_multidim() {
         check("void f()\n"
               "{\n"
diff --git a/test/testnullpointer.cpp b/test/testnullpointer.cpp
index f984b5aac..217e72405 100644
--- a/test/testnullpointer.cpp
+++ b/test/testnullpointer.cpp
@@ -2752,6 +2752,15 @@ private:
               "        return 0;\n"
               "}");
         ASSERT_EQUALS("[test.cpp:7]: (error) Null pointer dereference: myNull\n", errout.str());
+
+        check("struct T { bool g() const; };\n"
+              "void f(T* p) {\n"
+              "    if (!p)\n"
+              "        return;\n"
+              "    while (p->g())\n"
+              "        p = nullptr;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:5]: (warning) Possible null pointer dereference: p\n", errout.str());
     }
 
     void nullpointer94() // #11040
diff --git a/test/teststring.cpp b/test/teststring.cpp
index 8d443e215..b4d8d8156 100644
--- a/test/teststring.cpp
+++ b/test/teststring.cpp
@@ -798,6 +798,14 @@ private:
               "    ASSERT((void*)(\"def\") == 0);\n"
               "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        check("class C {\n" // #6109
+              "    void check(const char code[], bool validate = true, const char* filename = \"test.cpp\");\n"
+              "    void f() {\n"
+              "        check(\"class A<B&, C>;\", \"test.C\");\n"
+              "    }\n"
+              "};\n");
+        ASSERT_EQUALS("[test.cpp:4]: (warning) Conversion of string literal \"test.C\" to bool always evaluates to true.\n", errout.str());
     }
 
     void deadStrcmp() {