Add additional UTF-8 unit test corner cases. (#30406)

* Add additional UTF-8 unit test corner cases.

- Add more corner cases around overlong strings and UTF-16
  surrogate pairs that cannot happen in UTF-8.
- Fixed suite name.
- Thankfully, all tests still pass :)

* Restyled by clang-format

* Update src/lib/support/tests/TestUtf8.cpp

---------

Co-authored-by: Restyled.io <commits@restyled.io>

src/lib/support/tests/TestUtf8.cpp

@@ -28,6 +28,22 @@ namespace {
 
 using namespace chip;
 
+#define TEST_VALID_BYTES(...) \
+ do \
+ { \
+ uint8_t _buff[] = { __VA_ARGS__ }; \
+ CharSpan _span(reinterpret_cast<const char *>(_buff), sizeof(_buff)); \
+ NL_TEST_ASSERT(inSuite, Utf8::IsValid(_span)); \
+ } while (0)
+
+#define TEST_INVALID_BYTES(...) \
+ do \
+ { \
+ uint8_t _buff[] = { __VA_ARGS__ }; \
+ CharSpan _span(reinterpret_cast<const char *>(_buff), sizeof(_buff)); \
+ NL_TEST_ASSERT(inSuite, !Utf8::IsValid(_span)); \
+ } while (0)
+
 void TestValidStrings(nlTestSuite * inSuite, void * inContext)
 {
  NL_TEST_ASSERT(inSuite, Utf8::IsValid(CharSpan())); // empty span ok
@@ -80,23 +96,26 @@ void TestValidStrings(nlTestSuite * inSuite, void * inContext)
  char insideZero[] = "test\0zero";
  NL_TEST_ASSERT(inSuite, Utf8::IsValid(CharSpan(insideZero)));
  }
-}
 
-#define TEST_INVALID_BYTES(...) \
- { \
- uint8_t _buff[] = { __VA_ARGS__ }; \
- CharSpan _span(reinterpret_cast<const char *>(_buff), sizeof(_buff)); \
- NL_TEST_ASSERT(inSuite, !Utf8::IsValid(_span)); \
- } \
- (void) 0
+ // Test around forbidden 0xD800..0xDFFF UTF-16 surrogate pairs.
+ TEST_VALID_BYTES(0b1110'1101, 0b10'011111, 0b10'111111);
+ TEST_VALID_BYTES(0b1110'1110, 0b10'000000, 0b10'000000);
+}
 
 void TestInvalidStrings(nlTestSuite * inSuite, void * inContext)
 {
- // overly long representation
+ // Overly long sequences
+ TEST_INVALID_BYTES(0xc0, 0b10'111111);
+ TEST_INVALID_BYTES(0xc1, 0b10'111111);
+
  TEST_INVALID_BYTES(0xe0, 0b1001'1111, 0x80); // A
  TEST_INVALID_BYTES(0xed, 0b1011'0000, 0x80); // B
  TEST_INVALID_BYTES(0xf0, 0b1000'1111, 0x80); // C
 
+ // Invalid 0xD800 .. 0xDFFF UTF-16 surrogates that should not appear in UTF-8.
+ TEST_INVALID_BYTES(0b1110'1101, 0b10'100000, 0b10'000000);
+ TEST_INVALID_BYTES(0b1110'1101, 0b10'111111, 0b10'111111);
+
  // Outside codepoint
  TEST_INVALID_BYTES(0xf4, 0x90, 0x80, 0x80); // D
  TEST_INVALID_BYTES(0xf4, 0x91, 0x82, 0x83);
@@ -162,7 +181,8 @@ const nlTest sTests[] =
 
 int TestUtf8()
 {
- nlTestSuite theSuite = { "CHIP UTF8 tests", &sTests[0], nullptr, nullptr };
+ nlTestSuite theSuite = { "UTF8 validator tests", &sTests[0], nullptr, nullptr };
+
  nlTestRunner(&theSuite, nullptr);
  return nlTestRunnerStats(&theSuite);
 }