Converted StringBuilder tests to gtest

tests/StringBuilderTests.cpp

@@ -0,0 +1,76 @@
+#include <gtest/gtest.h>
+
+#include "StringBuilder.h"
+
+using namespace ArduinoJson::Internals;
+
+class StringBuilderTests : public testing::Test
+{
+protected:
+    
+    virtual void SetUp()
+    {
+        sb = new StringBuilder(buffer, sizeof(buffer));
+    }
+
+    void print(const char* value)
+    {
+        returnValue = sb->print(value);
+    }
+
+    void outputMustBe(const char* expected)
+    {
+        EXPECT_STREQ(expected, buffer);
+    }
+
+    void resultMustBe(size_t expected)
+    {
+        EXPECT_EQ(expected, returnValue);
+    }
+
+private:
+    char buffer[20];
+    Print* sb;
+    size_t returnValue;
+};
+
+TEST_F(StringBuilderTests, InitialState)
+{
+    outputMustBe("");
+}
+
+TEST_F(StringBuilderTests, OverCapacity)
+{
+    print("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
+    resultMustBe(19);
+
+    print("ABC");
+    resultMustBe(0);
+
+    outputMustBe("ABCDEFGHIJKLMNOPQRS");
+}
+
+TEST_F(StringBuilderTests, EmptyString)
+{
+    print("");
+    resultMustBe(0);
+    outputMustBe("");
+}
+
+TEST_F(StringBuilderTests, OneString)
+{
+    print("ABCD");
+    resultMustBe(4);
+    outputMustBe("ABCD");
+}
+
+TEST_F(StringBuilderTests, TwoStrings)
+{
+    print("ABCD");
+    resultMustBe(4);
+
+    print("EFGH");
+    resultMustBe(4);
+
+    outputMustBe("ABCDEFGH");
+}