Introduce BackspaceStateMachine

third_party/WebKit/Source/core/editing/BackspaceStateMachineTest.cpp

+// Copyright 2016 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 "core/editing/BackspaceStateMachine.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace blink {
+
+TEST(BackspaceStateMachineTest, DoNothingCase)
+{
+    BackspaceStateMachine machine;
+    EXPECT_EQ(0, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(0, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+}
+
+TEST(BackspaceStateMachineTest, SingleCharacter)
+{
+    BackspaceStateMachine machine;
+    EXPECT_TRUE(machine.updateState('a'));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+
+    machine.reset();
+    EXPECT_TRUE(machine.updateState('-'));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+
+    machine.reset();
+    EXPECT_TRUE(machine.updateState('\t'));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+
+    machine.reset();
+    // U+3042 HIRAGANA LETTER A.
+    EXPECT_TRUE(machine.updateState(0x3042));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+}
+
+TEST(BackspaceStateMachineTest, SurrogatePair)
+{
+    BackspaceStateMachine machine;
+
+    // U+1F5FA(WORLD MAP) is \uD83D\uDDFA in UTF-16.
+    uint16_t leadSurrogate = 0xD83D;
+    uint16_t trailSurrogate = 0xDDFA;
+
+    EXPECT_FALSE(machine.updateState(trailSurrogate));
+    EXPECT_TRUE(machine.updateState(leadSurrogate));
+    EXPECT_EQ(2, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(2, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+
+    // Edge cases
+    // Unpaired trailing surrogate. Delete only broken trail surrogate.
+    machine.reset();
+    EXPECT_FALSE(machine.updateState(trailSurrogate));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+
+    machine.reset();
+    EXPECT_FALSE(machine.updateState(trailSurrogate));
+    EXPECT_TRUE(machine.updateState('a'));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+
+    machine.reset();
+    EXPECT_FALSE(machine.updateState(trailSurrogate));
+    EXPECT_TRUE(machine.updateState(trailSurrogate));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+
+    // Unpaired leading surrogate. Delete only broken lead surrogate.
+    machine.reset();
+    EXPECT_TRUE(machine.updateState(leadSurrogate));
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+    EXPECT_EQ(1, machine.finalizeAndGetCodeUnitCountToBeDeleted());
+}
+
+} // namespace blink