Add few basic unit tests for DateValue

I feel more confortable doing changes in a code that I do not know by
having some unit tests around it. These characterisation tests will
also be useful as documentation.

unitTests/CMakeLists.txt

@@ -6,6 +6,7 @@ add_executable(unit_tests mainTestRunner.cpp
     test_enforce.cpp
     test_safe_op.cpp
     test_XmpKey.cpp
+    test_DateValue.cpp
 )
 
 #TODO Use GTest::GTest once we upgrade the minimum CMake version required

unitTests/test_DateValue.cpp

@@ -0,0 +1,81 @@
+#include "value.hpp"
+
+#include "gtestwrapper.h"
+
+using namespace Exiv2;
+
+TEST(ADateValue, isDefaultConstructed)
+{
+    const DateValue dateValue;
+    ASSERT_EQ(0, dateValue.getDate().year);
+    ASSERT_EQ(0, dateValue.getDate().month);
+    ASSERT_EQ(0, dateValue.getDate().day);
+}
+
+TEST(ADateValue, isConstructedWithArgs)
+{
+    const DateValue dateValue (2018, 4, 2);
+    ASSERT_EQ(2018, dateValue.getDate().year);
+    ASSERT_EQ(4, dateValue.getDate().month);
+    ASSERT_EQ(2, dateValue.getDate().day);
+}
+
+
+TEST(ADateValue, readFromByteBufferWithExpectedSize)
+{
+    DateValue dateValue;
+    const byte date[8] = {0x32, 0x30, 0x31, 0x38, 0x30, 0x34, 0x30, 0x32 }; // 20180402
+    ASSERT_EQ(0, dateValue.read(date, 8));
+    ASSERT_EQ(2018, dateValue.getDate().year);
+    ASSERT_EQ(4, dateValue.getDate().month);
+    ASSERT_EQ(2, dateValue.getDate().day);
+}
+
+TEST(ADateValue, doNotReadFromByteBufferWithoutExpectedSize)
+{
+    DateValue dateValue;
+    const byte date[8] = {0x32, 0x30, 0x31, 0x38, 0x30, 0x34, 0x30, 0x32 }; // 20180402
+    ASSERT_EQ(1, dateValue.read(date, 9));
+}
+
+TEST(ADateValue, doNotReadFromByteBufferWithExpectedSizeButNotCorrectContent)
+{
+    DateValue dateValue;
+    const byte date[8] = {0x32, 0x30, 0x31, 0x38, 0x30, 0x34, 0x23, 0x23 }; // 201804##
+    ASSERT_EQ(1, dateValue.read(date, 8));
+}
+
+
+TEST(ADateValue, readFromStringWithExpectedSize)
+{
+    DateValue dateValue;
+    const std::string date ("2018-04-02");
+    ASSERT_EQ(0, dateValue.read(date));
+    ASSERT_EQ(2018, dateValue.getDate().year);
+    ASSERT_EQ(4, dateValue.getDate().month);
+    ASSERT_EQ(2, dateValue.getDate().day);
+}
+
+TEST(ADateValue, doNotReadFromStringWithoutExpectedSize)
+{
+    DateValue dateValue;
+    const std::string date ("20180402");
+    ASSERT_EQ(1, dateValue.read(date));
+}
+
+TEST(ADateValue, doNotReadFromStringWithExpectedSizeButNotCorrectContent)
+{
+    DateValue dateValue;
+    const std::string date ("2018-aa-bb");
+    ASSERT_EQ(1, dateValue.read(date));
+}
+
+
+
+TEST(ADateValue, copyToByteBuffer)
+{
+    const DateValue dateValue (2018, 4, 2);
+    byte buffer[9];
+    ASSERT_EQ(8, dateValue.copy(buffer));
+    ASSERT_STREQ("20180402", reinterpret_cast<const char *>(buffer));
+}