Add unittests for different transport security state generator components.

net/tools/transport_security_state_generator/bit_writer_unittest.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/tools/transport_security_state_generator/bit_writer.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+
+namespace transport_security_state {
+

[Ryan Sleevi, 2017/03/30 15:03:32]

A common idiom is to put these tests in an extra (unnamed) namespace, to avoid
any ODR violations. If two tests end up sharing the same name, GTest will barf,
but if they're left in the same namespace, the compiler/linker will potentially
ODR-out one of them.

In general, the pattern in //net is to only leave them in the 'parent' namespace
if they're forward-declared fixtures.

But that's more of a nit, and if that style has changed out from under me,
please do let me know and don't feel you have to make that change :)

[martijnc, 2017/03/30 19:02:22]

I put them in an extra namespace, this still seems the common pattern in //net
and I'm not aware of any recent changes :).

+// Test that single bits are written to the buffer correctly.
+TEST(BitWriterTest, WriteBit) {
+  BitWriter writer;
+
+  EXPECT_EQ(0U, writer.position());
+  EXPECT_EQ(0U, writer.bytes().size());
+
+  writer.WriteBit(0);
+
+  EXPECT_EQ(1U, writer.position());
+
+  writer.WriteBit(1);
+  writer.WriteBit(0);
+  writer.WriteBit(1);
+  writer.WriteBit(0);
+  writer.WriteBit(1);
+  writer.WriteBit(0);
+  writer.WriteBit(1);
+
+  EXPECT_EQ(8U, writer.position());
+
+  writer.WriteBit(0);
+
+  EXPECT_EQ(9U, writer.position());
+
+  writer.WriteBit(1);
+  writer.WriteBit(0);
+
+  EXPECT_EQ(11U, writer.position());
+
+  // Flush should pad the current byte with zero's until it's full.
+  writer.Flush();
+
+  // The writer should have 2 bytes now even though we only wrote 11 bits.
+  EXPECT_EQ(16U, writer.position());
+
+  // 0 + 1 + 0 + 1 + 0 + 1 + 0 + 1 + 0 + 1 + 0  + 00000 (padding) = 0x5540.
+  EXPECT_THAT(writer.bytes(), testing::ElementsAre(0x55, 0x40));
+}
+
+// Test that when multiple bits are written to the buffer, they are appended
+// correctly.
+TEST(BitWriterTest, WriteBits) {
+  BitWriter writer;
+
+  writer.WriteBits(170, 1);

[Ryan Sleevi, 2017/03/30 15:03:32]

It took a quick consult of the table to find out 170 was 1010101010. I'm not
sure if 0xAA would have been clearer (I suppose only if you spend time
reversing), but maybe worth a comment here on the binary value :)

If only we had C++14 binary literals :)

[martijnc, 2017/03/30 19:02:22]

Added a comment and replaced 170 with 0xAA.

+  EXPECT_EQ(1U, writer.position());
+  writer.WriteBits(170, 2);
+  EXPECT_EQ(3U, writer.position());
+  writer.WriteBits(170, 3);
+  EXPECT_EQ(6U, writer.position());
+  writer.WriteBits(170, 2);
+  EXPECT_EQ(8U, writer.position());
+  writer.WriteBits(170, 2);
+  EXPECT_EQ(10U, writer.position());
+
+  // Flush should pad the current byte with zero's until it's full.
+  writer.Flush();
+
+  // The writer should have 2 bytes now even though we only wrote 10 bits.
+  EXPECT_EQ(16U, writer.position());
+
+  // 0 + 10 + 010 + 10 + 10 + 000000 (padding) = 0x4A80
+  EXPECT_THAT(writer.bytes(), testing::ElementsAre(0x4A, 0x80));
+}
+
+// Test that buffering works correct when the methods are mixed.
+TEST(BitWriterTest, WriteBoth) {
+  BitWriter writer;
+
+  writer.WriteBits(170, 1);
+  EXPECT_EQ(1U, writer.position());
+  writer.WriteBit(1);
+  writer.WriteBits(170, 2);
+  EXPECT_EQ(4U, writer.position());
+  writer.WriteBits(170, 3);
+  EXPECT_EQ(7U, writer.position());
+  writer.WriteBit(1);
+  EXPECT_EQ(8U, writer.position());
+
+  writer.WriteBits(170, 2);
+  writer.WriteBit(0);
+  EXPECT_EQ(11U, writer.position());
+
+  // Flush should pad the current byte with zero's until it's full.
+  writer.Flush();
+
+  // The writer should have 2 bytes now even though we only wrote 10 bits.
+  EXPECT_EQ(16U, writer.position());
+
+  // 0 + 1 + 10 + 010 + 1 + 10 + 0 + 00000 (padding) = 0x6580
+  EXPECT_THAT(writer.bytes(), testing::ElementsAre(0x65, 0x80));
+}
+
+}  // transport_security_state
+
+}  // namespace net