Removed implicit conversion in comparison operators (issue #998)

CHANGELOG.md

@@ -9,6 +9,8 @@ HEAD
 * Made `deserializeJson()` more picky about trailing characters (issue #980)
 * Added `ARDUINOJSON_ENABLE_NAN` (default=0) to enable NaN in JSON (issue #973)
 * Added `ARDUINOJSON_ENABLE_INFINITY` (default=0) to enable Infinity in JSON
+* Removed implicit conversion in comparison operators (issue #998)
+* Added lexicographical comparison for `JsonVariant`
 
 > ### BREAKING CHANGES
 > 

src/ArduinoJson/Operators/VariantComparisons.hpp

@@ -7,154 +7,216 @@
 #include "../Variant/VariantRef.hpp"
 
 namespace ARDUINOJSON_NAMESPACE {
+
+template <typename T, typename Enable = void>
+struct Comparer;
+
 template <typename T>
-struct is_simple_value {
-  static const bool value = is_integral<T>::value ||
-                            is_floating_point<T>::value ||
-                            is_same<T, bool>::value;
+struct Comparer<T, typename enable_if<IsString<T>::value>::type> {
+  T rhs;
+  int result;
+
+  explicit Comparer(T value) : rhs(value), result(1) {}
+
+  void visitArray(const CollectionData &) {}
+  void visitObject(const CollectionData &) {}
+  void visitFloat(Float) {}
+  void visitString(const char *lhs) {
+    result = -adaptString(rhs).compare(lhs);
+  }
+  void visitRawJson(const char *, size_t) {}
+  void visitNegativeInteger(UInt) {}
+  void visitPositiveInteger(UInt) {}
+  void visitBoolean(bool) {}
+  void visitNull() {
+    result = adaptString(rhs).compare(NULL);
+  }
+};
+
+template <typename T>
+typename enable_if<is_signed<T>::value, int>::type sign(const T &value) {
+  return value < 0 ? -1 : value > 0 ? 1 : 0;
+}
+
+template <typename T>
+typename enable_if<is_unsigned<T>::value, int>::type sign(const T &value) {
+  return value > 0 ? 1 : 0;
+}
+
+template <typename T>
+struct Comparer<T, typename enable_if<is_integral<T>::value ||
+                                      is_floating_point<T>::value>::type> {
+  T rhs;
+  int result;
+
+  explicit Comparer(T value) : rhs(value), result(1) {}
+
+  void visitArray(const CollectionData &) {}
+  void visitObject(const CollectionData &) {}
+  void visitFloat(Float lhs) {
+    result = sign(lhs - static_cast<Float>(rhs));
+  }
+  void visitString(const char *) {}
+  void visitRawJson(const char *, size_t) {}
+  void visitNegativeInteger(UInt lhs) {
+    result = -sign(static_cast<T>(lhs) + rhs);
+  }
+  void visitPositiveInteger(UInt lhs) {
+    result = static_cast<T>(lhs) < rhs ? -1 : static_cast<T>(lhs) > rhs ? 1 : 0;
+  }
+  void visitBoolean(bool) {}
+  void visitNull() {}
+};
+
+template <>
+struct Comparer<bool, void> {
+  bool rhs;
+  int result;
+
+  explicit Comparer(bool value) : rhs(value), result(1) {}
+
+  void visitArray(const CollectionData &) {}
+  void visitObject(const CollectionData &) {}
+  void visitFloat(Float) {}
+  void visitString(const char *) {}
+  void visitRawJson(const char *, size_t) {}
+  void visitNegativeInteger(UInt) {}
+  void visitPositiveInteger(UInt) {}
+  void visitBoolean(bool lhs) {
+    result = static_cast<int>(lhs - rhs);
+  }
+  void visitNull() {}
 };
 
 template <typename TVariant>
 class VariantComparisons {
+ private:
+  template <typename T>
+  static int compare(TVariant lhs, const T &rhs) {
+    Comparer<T> comparer(rhs);
+    lhs.accept(comparer);
+    return comparer.result;
+  }
+
  public:
-  // const char* == TVariant
+  // value == TVariant
   template <typename T>
-  friend typename enable_if<IsString<T *>::value, bool>::type operator==(
-      T *lhs, TVariant rhs) {
-    return adaptString(lhs).equals(rhs.template as<const char *>());
+  friend bool operator==(T *lhs, TVariant rhs) {
+    return compare(rhs, lhs) == 0;
+  }
+  template <typename T>
+  friend bool operator==(const T &lhs, TVariant rhs) {
+    return compare(rhs, lhs) == 0;
   }
 
-  // std::string == TVariant
+  // TVariant == value
   template <typename T>
-  friend typename enable_if<IsString<T>::value, bool>::type operator==(
-      const T &lhs, TVariant rhs) {
-    return adaptString(lhs).equals(rhs.template as<const char *>());
+  friend bool operator==(TVariant lhs, T *rhs) {
+    return compare(lhs, rhs) == 0;
+  }
+  template <typename T>
+  friend bool operator==(TVariant lhs, const T &rhs) {
+    return compare(lhs, rhs) == 0;
   }
 
-  // TVariant == const char*
+  // value != TVariant
   template <typename T>
-  friend typename enable_if<IsString<T *>::value, bool>::type operator==(
-      TVariant lhs, T *rhs) {
-    return adaptString(rhs).equals(lhs.template as<const char *>());
+  friend bool operator!=(T *lhs, TVariant rhs) {
+    return compare(rhs, lhs) != 0;
+  }
+  template <typename T>
+  friend bool operator!=(const T &lhs, TVariant rhs) {
+    return compare(rhs, lhs) != 0;
   }
 
-  // TVariant == std::string
+  // TVariant != value
   template <typename T>
-  friend typename enable_if<IsString<T>::value, bool>::type operator==(
-      TVariant lhs, const T &rhs) {
-    return adaptString(rhs).equals(lhs.template as<const char *>());
+  friend bool operator!=(TVariant lhs, T *rhs) {
+    return compare(lhs, rhs) != 0;
+  }
+  template <typename T>
+  friend bool operator!=(TVariant lhs, const T &rhs) {
+    return compare(lhs, rhs) != 0;
   }
 
-  // bool/int/float == TVariant
+  // value < TVariant
   template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator==(
-      const T &lhs, TVariant rhs) {
-    return lhs == rhs.template as<T>();
+  friend bool operator<(T *lhs, TVariant rhs) {
+    return compare(rhs, lhs) > 0;
+  }
+  template <typename T>
+  friend bool operator<(const T &lhs, TVariant rhs) {
+    return compare(rhs, lhs) > 0;
   }
 
-  // TVariant == bool/int/float
+  // TVariant < value
   template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator==(
-      TVariant lhs, const T &rhs) {
-    return lhs.template as<T>() == rhs;
+  friend bool operator<(TVariant lhs, T *rhs) {
+    return compare(lhs, rhs) < 0;
+  }
+  template <typename T>
+  friend bool operator<(TVariant lhs, const T &rhs) {
+    return compare(lhs, rhs) < 0;
   }
 
-  // const char* != TVariant
+  // value <= TVariant
   template <typename T>
-  friend typename enable_if<IsString<T *>::value, bool>::type operator!=(
-      T *lhs, TVariant rhs) {
-    return !adaptString(lhs).equals(rhs.template as<const char *>());
+  friend bool operator<=(T *lhs, TVariant rhs) {
+    return compare(rhs, lhs) >= 0;
+  }
+  template <typename T>
+  friend bool operator<=(const T &lhs, TVariant rhs) {
+    return compare(rhs, lhs) >= 0;
   }
 
-  // std::string != TVariant
+  // TVariant <= value
   template <typename T>
-  friend typename enable_if<IsString<T>::value, bool>::type operator!=(
-      const T &lhs, TVariant rhs) {
-    return !adaptString(lhs).equals(rhs.template as<const char *>());
+  friend bool operator<=(TVariant lhs, T *rhs) {
+    return compare(lhs, rhs) <= 0;
+  }
+  template <typename T>
+  friend bool operator<=(TVariant lhs, const T &rhs) {
+    return compare(lhs, rhs) <= 0;
   }
 
-  // TVariant != const char*
+  // value > TVariant
   template <typename T>
-  friend typename enable_if<IsString<T *>::value, bool>::type operator!=(
-      TVariant lhs, T *rhs) {
-    return !adaptString(rhs).equals(lhs.template as<const char *>());
+  friend bool operator>(T *lhs, TVariant rhs) {
+    return compare(rhs, lhs) < 0;
+  }
+  template <typename T>
+  friend bool operator>(const T &lhs, TVariant rhs) {
+    return compare(rhs, lhs) < 0;
   }
 
-  // TVariant != std::string
+  // TVariant > value
   template <typename T>
-  friend typename enable_if<IsString<T>::value, bool>::type operator!=(
-      TVariant lhs, const T &rhs) {
-    return !adaptString(rhs).equals(lhs.template as<const char *>());
+  friend bool operator>(TVariant lhs, T *rhs) {
+    return compare(lhs, rhs) > 0;
+  }
+  template <typename T>
+  friend bool operator>(TVariant lhs, const T &rhs) {
+    return compare(lhs, rhs) > 0;
   }
 
-  // bool/int/float != TVariant
+  // value >= TVariant
   template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator!=(
-      const T &lhs, TVariant rhs) {
-    return lhs != rhs.template as<T>();
+  friend bool operator>=(T *lhs, TVariant rhs) {
+    return compare(rhs, lhs) <= 0;
+  }
+  template <typename T>
+  friend bool operator>=(const T &lhs, TVariant rhs) {
+    return compare(rhs, lhs) <= 0;
   }
 
-  // TVariant != bool/int/float
+  // TVariant >= value
   template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator!=(
-      TVariant lhs, const T &rhs) {
-    return lhs.template as<T>() != rhs;
+  friend bool operator>=(TVariant lhs, T *rhs) {
+    return compare(lhs, rhs) >= 0;
   }
-
-  // bool/int/float < TVariant
   template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator<(
-      const T &lhs, TVariant rhs) {
-    return lhs < rhs.template as<T>();
-  }
-
-  // TVariant < bool/int/float
-  template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator<(
-      TVariant lhs, const T &rhs) {
-    return lhs.template as<T>() < rhs;
-  }
-
-  // bool/int/float <= TVariant
-  template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator<=(
-      const T &lhs, TVariant rhs) {
-    return lhs <= rhs.template as<T>();
-  }
-
-  // TVariant <= bool/int/float
-  template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator<=(
-      TVariant lhs, const T &rhs) {
-    return lhs.template as<T>() <= rhs;
-  }
-
-  // bool/int/float > TVariant
-  template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator>(
-      const T &lhs, TVariant rhs) {
-    return lhs > rhs.template as<T>();
-  }
-
-  // TVariant > bool/int/float
-  template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator>(
-      TVariant lhs, const T &rhs) {
-    return lhs.template as<T>() > rhs;
-  }
-
-  // bool/int/float >= TVariant
-  template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator>=(
-      const T &lhs, TVariant rhs) {
-    return lhs >= rhs.template as<T>();
-  }
-
-  // TVariant >= bool/int/float
-  template <typename T>
-  friend typename enable_if<is_simple_value<T>::value, bool>::type operator>=(
-      TVariant lhs, const T &rhs) {
-    return lhs.template as<T>() >= rhs;
+  friend bool operator>=(TVariant lhs, const T &rhs) {
+    return compare(lhs, rhs) >= 0;
   }
 };
 

src/ArduinoJson/Polyfills/safe_strcmp.hpp

@@ -0,0 +1,22 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#pragma once
+
+namespace ARDUINOJSON_NAMESPACE {
+
+inline int8_t safe_strcmp(const char* a, const char* b) {
+  if (a == b) return 0;
+  if (!a) return -1;
+  if (!b) return 1;
+  return static_cast<int8_t>(strcmp(a, b));
+}
+
+inline int8_t safe_strncmp(const char* a, const char* b, size_t n) {
+  if (a == b) return 0;
+  if (!a) return -1;
+  if (!b) return 1;
+  return static_cast<int8_t>(strncmp(a, b, n));
+}
+}  // namespace ARDUINOJSON_NAMESPACE

src/ArduinoJson/Strings/ArduinoStringAdapter.hpp

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <WString.h>
+#include "../Polyfills/safe_strcmp.hpp"
 
 namespace ARDUINOJSON_NAMESPACE {
 
@@ -25,11 +26,14 @@ class ArduinoStringAdapter {
     return !_str->c_str();
   }
 
-  bool equals(const char* expected) const {
+  int8_t compare(const char* other) const {
     // Arduino's String::c_str() can return NULL
-    const char* actual = _str->c_str();
-    if (!actual || !expected) return actual == expected;
-    return 0 == strcmp(actual, expected);
+    const char* me = _str->c_str();
+    return safe_strcmp(me, other);
+  }
+
+  bool equals(const char* expected) const {
+    return compare(expected) == 0;
   }
 
   const char* data() const {

src/ArduinoJson/Strings/ConstRamStringAdapter.hpp

@@ -6,6 +6,7 @@
 
 #include <stddef.h>  // size_t
 #include <string.h>  // strcmp
+#include "../Polyfills/safe_strcmp.hpp"
 
 namespace ARDUINOJSON_NAMESPACE {
 
@@ -13,10 +14,12 @@ class ConstRamStringAdapter {
  public:
   ConstRamStringAdapter(const char* str = 0) : _str(str) {}
 
+  int8_t compare(const char* other) const {
+    return safe_strcmp(_str, other);
+  }
+
   bool equals(const char* expected) const {
-    const char* actual = _str;
-    if (!actual || !expected) return actual == expected;
-    return strcmp(actual, expected) == 0;
+    return compare(expected) == 0;
   }
 
   bool isNull() const {

src/ArduinoJson/Strings/FlashStringAdapter.hpp

@@ -10,10 +10,15 @@ class FlashStringAdapter {
  public:
   FlashStringAdapter(const __FlashStringHelper* str) : _str(str) {}
 
+  int8_t compare(const char* other) const {
+    if (!other && !_str) return 0;
+    if (!_str) return -1;
+    if (!other) return 1;
+    return -strcmp_P(other, reinterpret_cast<const char*>(_str));
+  }
+
   bool equals(const char* expected) const {
-    const char* actual = reinterpret_cast<const char*>(_str);
-    if (!actual || !expected) return actual == expected;
-    return strcmp_P(expected, actual) == 0;
+    return compare(expected) == 0;
   }
 
   bool isNull() const {

src/ArduinoJson/Strings/SizedFlashStringAdapter.hpp

@@ -11,10 +11,15 @@ class SizedFlashStringAdapter {
   SizedFlashStringAdapter(const __FlashStringHelper* str, size_t sz)
       : _str(str), _size(sz) {}
 
+  int8_t compare(const char* other) const {
+    if (!other && !_str) return 0;
+    if (!_str) return -1;
+    if (!other) return 1;
+    return -strncmp_P(other, reinterpret_cast<const char*>(_str), _size);
+  }
+
   bool equals(const char* expected) const {
-    const char* actual = reinterpret_cast<const char*>(_str);
-    if (!actual || !expected) return actual == expected;
-    return strncmp_P(expected, actual, _size) == 0;
+    return compare(expected) == 0;
   }
 
   bool isNull() const {

src/ArduinoJson/Strings/SizedRamStringAdapter.hpp

@@ -12,10 +12,12 @@ class SizedRamStringAdapter {
  public:
   SizedRamStringAdapter(const char* str, size_t n) : _str(str), _size(n) {}
 
+  int8_t compare(const char* other) const {
+    return safe_strncmp(_str, other, _size) == 0;
+  }
+
   bool equals(const char* expected) const {
-    const char* actual = reinterpret_cast<const char*>(_str);
-    if (!actual || !expected) return actual == expected;
-    return strcmp(actual, expected) == 0;
+    return compare(expected) == 0;
   }
 
   bool isNull() const {

src/ArduinoJson/Strings/StlStringAdapter.hpp

@@ -23,6 +23,11 @@ class StlStringAdapter {
     return false;
   }
 
+  int8_t compare(const char* other) const {
+    if (!other) return 1;
+    return static_cast<int8_t>(_str->compare(other));
+  }
+
   bool equals(const char* expected) const {
     if (!expected) return false;
     return *_str == expected;

test/JsonObject/subscript.cpp

@@ -161,7 +161,7 @@ TEST_CASE("JsonObject::operator[]") {
     obj[null] = 666;
 
     REQUIRE(obj.size() == 1);
-    REQUIRE(obj[null] == 0);
+    REQUIRE(obj[null] == null);
   }
 
   SECTION("obj[key].to<JsonArray>()") {

test/JsonVariant/compare.cpp

@@ -337,23 +337,117 @@ TEST_CASE("JsonVariant comparisons") {
     REQUIRE(variant1 != variant3);
     REQUIRE_FALSE(variant1 == variant3);
   }
-
-  // SECTION("VariantsOfDifferentTypes") {
-  //   DynamicJsonDocument doc1(4096);
-  //   JsonObject obj = doc1.to<JsonObject>();
-
-  //   DynamicJsonDocument doc2(4096);
-  //   JsonArray arr = doc2.to<JsonArray>();
-  //   JsonVariant variants[] = {
-  //       true, 42, 666.667, "hello", arr, obj,
-  //   };
-  //   size_t n = sizeof(variants) / sizeof(variants[0]);
-
-  //   for (size_t i = 0; i < n; i++) {
-  //     for (size_t j = i + 1; j < n; j++) {
-  //       REQUIRE(variants[i] != variants[j]);
-  //       REQUIRE_FALSE(variants[i] == variants[j]);
-  //     }
-  //   }
-  // }
+}
+
+class VariantComparisionFixture {
+ private:
+  StaticJsonDocument<256> doc;
+  JsonVariant variant;
+
+ public:
+  VariantComparisionFixture() : variant(doc.to<JsonVariant>()) {}
+
+ protected:
+  template <typename T>
+  void setValue(const T& value) {
+    variant.set(value);
+  }
+
+  template <typename T>
+  void assertEqualsTo(const T& value) {
+    REQUIRE(variant == value);
+    REQUIRE(value == variant);
+
+    REQUIRE_FALSE(variant != value);
+    REQUIRE_FALSE(value != variant);
+  }
+
+  template <typename T>
+  void assertDiffersFrom(const T& value) {
+    REQUIRE(variant != value);
+    REQUIRE(value != variant);
+
+    REQUIRE_FALSE(variant == value);
+    REQUIRE_FALSE(value == variant);
+  }
+
+  template <typename T>
+  void assertGreaterThan(const T& value) {
+    REQUIRE((variant > value));
+    REQUIRE((variant >= value));
+    REQUIRE(value < variant);
+    REQUIRE(value <= variant);
+
+    REQUIRE_FALSE((variant < value));
+    REQUIRE_FALSE((variant <= value));
+    REQUIRE_FALSE(value > variant);
+    REQUIRE_FALSE(value >= variant);
+  }
+
+  template <typename T>
+  void assertLowerThan(const T& value) {
+    REQUIRE(variant < value);
+    REQUIRE(variant <= value);
+    REQUIRE(value > variant);
+    REQUIRE(value >= variant);
+
+    REQUIRE_FALSE(variant > value);
+    REQUIRE_FALSE(variant >= value);
+    REQUIRE_FALSE(value < variant);
+    REQUIRE_FALSE(value <= variant);
+  }
+};
+
+TEST_CASE_METHOD(VariantComparisionFixture,
+                 "Compare variant with another type") {
+  SECTION("null") {
+    assertDiffersFrom(3);
+    assertDiffersFrom("world");
+  }
+
+  SECTION("string") {
+    setValue("hello");
+    assertEqualsTo("hello");
+    assertDiffersFrom(3);
+    assertDiffersFrom("world");
+    assertGreaterThan("helln");
+    assertLowerThan("hellp");
+  }
+
+  SECTION("positive integer") {
+    setValue(42);
+    assertEqualsTo(42);
+    assertDiffersFrom(43);
+    assertGreaterThan(41);
+    assertLowerThan(43);
+    assertDiffersFrom("world");
+  }
+
+  SECTION("negative integer") {
+    setValue(-42);
+    assertEqualsTo(-42);
+    assertDiffersFrom(42);
+    assertGreaterThan(-43);
+    assertLowerThan(-41);
+    assertDiffersFrom("world");
+  }
+
+  SECTION("double") {
+    setValue(42.0);
+    assertEqualsTo(42.0);
+    assertDiffersFrom(42.1);
+    assertGreaterThan(41.0);
+    assertLowerThan(43.0);
+    assertDiffersFrom("42.0");
+  }
+
+  SECTION("true") {
+    setValue(true);
+    assertEqualsTo(true);
+    assertDiffersFrom(false);
+    assertDiffersFrom(1);
+    assertDiffersFrom("true");
+    assertDiffersFrom(1.0);
+    assertGreaterThan(false);
+  }
 }

test/JsonVariant/createNested.cpp

@@ -14,7 +14,7 @@ TEST_CASE("JsonVariant::createNestedObject()") {
 
   SECTION("promotes to array") {
     JsonObject obj = variant.createNestedObject();
-    obj["value"] = "42";
+    obj["value"] = 42;
 
     REQUIRE(variant.is<JsonArray>() == true);
     REQUIRE(variant[0]["value"] == 42);
@@ -23,7 +23,7 @@ TEST_CASE("JsonVariant::createNestedObject()") {
 
   SECTION("works on MemberProxy") {
     JsonObject obj = variant["items"].createNestedObject();
-    obj["value"] = "42";
+    obj["value"] = 42;
 
     REQUIRE(variant["items"][0]["value"] == 42);
   }
@@ -42,7 +42,7 @@ TEST_CASE("JsonVariant::createNestedArray()") {
 
   SECTION("works on MemberProxy") {
     JsonArray arr = variant["items"].createNestedArray();
-    arr.add("42");
+    arr.add(42);
 
     REQUIRE(variant["items"][0][0] == 42);
   }
@@ -54,7 +54,7 @@ TEST_CASE("JsonVariant::createNestedObject(key)") {
 
   SECTION("promotes to object") {
     JsonObject obj = variant.createNestedObject("weather");
-    obj["temp"] = "42";
+    obj["temp"] = 42;
 
     REQUIRE(variant.is<JsonObject>() == true);
     REQUIRE(variant["weather"]["temp"] == 42);
@@ -62,7 +62,7 @@ TEST_CASE("JsonVariant::createNestedObject(key)") {
 
   SECTION("works on MemberProxy") {
     JsonObject obj = variant["status"].createNestedObject("weather");
-    obj["temp"] = "42";
+    obj["temp"] = 42;
 
     REQUIRE(variant["status"]["weather"]["temp"] == 42);
   }
@@ -81,7 +81,7 @@ TEST_CASE("JsonVariant::createNestedArray(key)") {
 
   SECTION("works on MemberProxy") {
     JsonArray arr = variant["weather"].createNestedArray("temp");
-    arr.add("42");
+    arr.add(42);
 
     REQUIRE(variant["weather"]["temp"][0] == 42);
   }

test/Misc/CMakeLists.txt

@@ -6,6 +6,7 @@ add_executable(MiscTests
 	conflicts.cpp
 	FloatParts.cpp
 	StreamReader.cpp
+	StringAdapters.cpp
 	StringWriter.cpp
 	TypeTraits.cpp
 	unsigned_char.cpp

test/Misc/StringAdapters.cpp

@@ -0,0 +1,45 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+using namespace ARDUINOJSON_NAMESPACE;
+
+TEST_CASE("ConstRamStringAdapter") {
+  SECTION("null") {
+    ConstRamStringAdapter adapter(NULL);
+
+    REQUIRE(adapter.compare("bravo") < 0);
+    REQUIRE(adapter.compare(NULL) == 0);
+
+    REQUIRE(adapter.equals(NULL));
+    REQUIRE_FALSE(adapter.equals("charlie"));
+  }
+
+  SECTION("non-null") {
+    ConstRamStringAdapter adapter("bravo");
+
+    REQUIRE(adapter.compare(NULL) > 0);
+    REQUIRE(adapter.compare("alpha") > 0);
+    REQUIRE(adapter.compare("bravo") == 0);
+    REQUIRE(adapter.compare("charlie") < 0);
+
+    REQUIRE(adapter.equals("bravo"));
+    REQUIRE_FALSE(adapter.equals("charlie"));
+  }
+}
+
+TEST_CASE("StlString") {
+  std::string str("bravo");
+  StlStringAdapter adapter(str);
+
+  REQUIRE(adapter.compare(NULL) > 0);
+  REQUIRE(adapter.compare("alpha") > 0);
+  REQUIRE(adapter.compare("bravo") == 0);
+  REQUIRE(adapter.compare("charlie") < 0);
+
+  REQUIRE(adapter.equals("bravo"));
+  REQUIRE_FALSE(adapter.equals("charlie"));
+}