[2850] Add tests to check that resetHeader() is called by ZoneWriter class

Initially I thought it was not possible to test this as
ZoneTableSegment::create() was used to create the zone table segment,
but it seems it's possible to do it this way using a mock class.

src/lib/datasrc/tests/memory/zone_writer_unittest.cc

@@ -38,10 +38,25 @@ namespace {
 
 class TestException {};
 
+class ZoneTableSegmentHelper : public ZoneTableSegmentMock {
+public:
+    ZoneTableSegmentHelper(const isc::dns::RRClass& rrclass,
+                           isc::util::MemorySegment& mem_sgmt) :
+        ZoneTableSegmentMock(rrclass, mem_sgmt),
+        reset_header_called_(false)
+    {}
+
+    virtual void resetHeader() {
+        reset_header_called_ = true;
+    }
+
+    bool reset_header_called_;
+};
+
 class ZoneWriterTest : public ::testing::Test {
 protected:
     ZoneWriterTest() :
-        segment_(ZoneTableSegment::create(RRClass::IN(), "local")),
+        segment_(new ZoneTableSegmentHelper(RRClass::IN(), mem_sgmt_)),
         writer_(new
             ZoneWriter(*segment_,
                        bind(&ZoneWriterTest::loadAction, this, _1),
@@ -55,7 +70,8 @@ protected:
         // Release the writer
         writer_.reset();
     }
-    scoped_ptr<ZoneTableSegment> segment_;
+    MemorySegmentMock mem_sgmt_;
+    scoped_ptr<ZoneTableSegmentHelper> segment_;
     scoped_ptr<ZoneWriter> writer_;
     bool load_called_;
     bool load_throw_;
@@ -123,14 +139,18 @@ TEST_F(ZoneWriterTest, constructForReadOnlySegment) {
 TEST_F(ZoneWriterTest, correctCall) {
     // Nothing called before we call it
     EXPECT_FALSE(load_called_);
+    EXPECT_FALSE(segment_->reset_header_called_);
 
     // Just the load gets called now
     EXPECT_NO_THROW(writer_->load());
     EXPECT_TRUE(load_called_);
+    EXPECT_TRUE(segment_->reset_header_called_);
     load_called_ = false;
+    segment_->reset_header_called_ = false;
 
     EXPECT_NO_THROW(writer_->install());
     EXPECT_FALSE(load_called_);
+    EXPECT_TRUE(segment_->reset_header_called_);
 
     // We don't check explicitly how this works, but call it to free memory. If
     // everything is freed should be checked inside the TearDown.
@@ -141,15 +161,19 @@ TEST_F(ZoneWriterTest, loadTwice) {
     // Load it the first time
     EXPECT_NO_THROW(writer_->load());
     EXPECT_TRUE(load_called_);
+    EXPECT_TRUE(segment_->reset_header_called_);
     load_called_ = false;
+    segment_->reset_header_called_ = false;
 
     // The second time, it should not be possible
     EXPECT_THROW(writer_->load(), isc::InvalidOperation);
     EXPECT_FALSE(load_called_);
+    EXPECT_FALSE(segment_->reset_header_called_);
 
     // The object should not be damaged, try installing and clearing now
     EXPECT_NO_THROW(writer_->install());
     EXPECT_FALSE(load_called_);
+    EXPECT_TRUE(segment_->reset_header_called_);
 
     // We don't check explicitly how this works, but call it to free memory. If
     // everything is freed should be checked inside the TearDown.
@@ -164,15 +188,18 @@ TEST_F(ZoneWriterTest, loadLater) {
     EXPECT_NO_THROW(writer_->install());
     // Reset so we see nothing is called now
     load_called_ = false;
+    segment_->reset_header_called_ = false;
 
     EXPECT_THROW(writer_->load(), isc::InvalidOperation);
     EXPECT_FALSE(load_called_);
+    EXPECT_FALSE(segment_->reset_header_called_);
 
     // Cleanup and try loading again. Still shouldn't work.
     EXPECT_NO_THROW(writer_->cleanup());
 
     EXPECT_THROW(writer_->load(), isc::InvalidOperation);
     EXPECT_FALSE(load_called_);
+    EXPECT_FALSE(segment_->reset_header_called_);
 }
 
 // Try calling install at various bad times