[C++] test message length functions

Author: Egor Seredin

sbe-tool/src/test/cpp/CodeGenTest.cpp

@@ -426,6 +426,25 @@ TEST_F(CodeGenTest, shouldBeAbleToEncodeCarCorrectly)
     offset += COLOR_LENGTH;
 
     EXPECT_EQ(sz, offset);
+
+    std::uint64_t predictedCarSz = Car::messageLength(
+        {
+            FUEL_FIGURES_1_USAGE_DESCRIPTION_LENGTH,
+            FUEL_FIGURES_2_USAGE_DESCRIPTION_LENGTH,
+            FUEL_FIGURES_3_USAGE_DESCRIPTION_LENGTH
+        },
+        {
+            ACCELERATION_COUNT,
+            ACCELERATION_COUNT
+        },
+        MANUFACTURER_LENGTH,
+        MODEL_LENGTH,
+        ACTIVATION_CODE_LENGTH,
+        COLOR_LENGTH
+    );
+    EXPECT_EQ(sz, predictedCarSz);
+    EXPECT_EQ(Car::isConstLength(), false);
+    EXPECT_EQ(Car::PerformanceFigures::Acceleration::isConstLength(), true);
 }
 
 TEST_F(CodeGenTest, shouldBeAbleToEncodeHeaderPlusCarCorrectly)

sbe-tool/src/test/cpp/CompositeElementsTest.cpp

@@ -210,6 +210,8 @@ TEST_F(CompositeElementsTest, shouldEncodeMsgCorrectly)
     std::uint64_t offset = 0;
 
     ASSERT_EQ(sz, 8u + 22u);
+    ASSERT_EQ(Msg::isConstLength(), true);
+    EXPECT_EQ(sz, Msg::sbeBlockAndHeaderLength());
 
     EXPECT_EQ(*((std::uint16_t *)(bufferPtr + offset)), Msg::sbeBlockLength());
     offset += sizeof(std::uint16_t);