Introduce ForwardGraphemeBoundaryStateMachine

third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachineTest.cpp

Index: third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachineTest.cpp
diff --git a/third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachineTest.cpp b/third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachineTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f27ecafce8abd8b3e7aee43e6fc2d2f93110a763
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachineTest.cpp
@@ -0,0 +1,629 @@
+// 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/state_machines/ForwardGraphemeBoundaryStateMachine.h"
+
+#include "core/editing/state_machines/StateMachineTestUtil.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "wtf/text/CharacterNames.h"
+
+namespace blink {
+
+// Notations:
+// | indicates inidicates initial offset position.
+// SOT indicates start of text.
+// EOT indicates end of text.
+// [Lead] indicates broken lonely lead surrogate.
+// [Trail] indicates broken lonely trail surrogate.
+// [U] indicates regional indicator symbol U.
+// [S] indicates regional indicator symbol S.
+
+namespace {
+// kWatch kVS16, kEye kVS16 are valid standardized variants.
+const UChar32 kWatch = 0x231A;
+const UChar32 kEye = WTF::Unicode::eyeCharacter;
+const UChar32 kVS16 = 0xFE0F;
+
+// kHanBMP KVS17, kHanSIP kVS17 are valie IVD sequences.
+const UChar32 kHanBMP = 0x845B;
+const UChar32 kHanSIP = 0x20000;
+const UChar32 kVS17 = 0xE0100;
+
+// Following lead/trail values are used for invalid surrogate pairs.
+const UChar kLead = 0xD83D;
+const UChar kTrail = 0xDC66;
+
+// U+1F1FA is REGIONAL INDICATOR SYMBOL LETTER U
+const UChar32 kRisU = 0x1F1FA;
+// U+1F1F8 is REGIONAL INDICATOR SYMBOL LETTER S
+const UChar32 kRisS = 0x1F1F8;
+} // namespace
+
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, DoNothingCase)
+{
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    EXPECT_EQ(0, machine.finalizeAndGetBoundaryOffset());
+    EXPECT_EQ(0, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, PrecedingText)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+    // Preceding text should not affect the result except for flags.
+    // SOT + | + 'a' + 'a'
+    EXPECT_EQ("SRF", processSequenceForward(&machine, kEmpty, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // SOT + [U] + | + 'a' + 'a'
+    EXPECT_EQ("RRSRF", processSequenceForward(&machine,
+        { kRisU }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // SOT + [U] + [S] + | + 'a' + 'a'
+    EXPECT_EQ("RRRRSRF", processSequenceForward(&machine,
+        { kRisU, kRisS }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + | + 'a' + 'a'
+    EXPECT_EQ("SRF", processSequenceForward(&machine, { 'a' }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // 'a' + [U] + | + 'a' + 'a'
+    EXPECT_EQ("RRSRF", processSequenceForward(&machine,
+        { 'a', kRisU }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // 'a' + [U] + [S] + | + 'a' + 'a'
+    EXPECT_EQ("RRRRSRF", processSequenceForward(&machine,
+        { 'a', kRisU, kRisS }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // U+1F441 + | + 'a' + 'a'
+    EXPECT_EQ("RSRF", processSequenceForward(&machine,
+        { kEye }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // U+1F441 + [U] + | + 'a' + 'a'
+    EXPECT_EQ("RRRSRF", processSequenceForward(&machine,
+        { kEye, kRisU }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // U+1F441 + [U] + [S] + | + 'a' + 'a'
+    EXPECT_EQ("RRRRRSRF", processSequenceForward(&machine,
+        { kEye, kRisU, kRisS }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // Broken surrogates in preceding text.
+
+    // [Lead] + | + 'a' + 'a'
+    EXPECT_EQ("SRF", processSequenceForward(&machine,
+        { kLead }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // [Lead] + [U] + | + 'a' + 'a'
+    EXPECT_EQ("RRSRF", processSequenceForward(&machine,
+        { kLead, kRisU }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // [Lead] + [U] + [S] + | + 'a' + 'a'
+    EXPECT_EQ("RRRRSRF", processSequenceForward(&machine,
+        { kLead, kRisU, kRisS }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [Trail] + | + 'a' + 'a'
+    EXPECT_EQ("RSRF", processSequenceForward(&machine,
+        { 'a', kTrail }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // 'a' + [Trail] + [U] + | + 'a' + 'a'
+    EXPECT_EQ("RRRSRF", processSequenceForward(&machine,
+        { 'a', kTrail, kRisU }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // 'a' + [Trail] + [U] + [S] + | + 'a' + 'a'
+    EXPECT_EQ("RRRRRSRF", processSequenceForward(&machine,
+        { 'a', kTrail, kRisU, kRisS }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // [Trail] + [Trail] + | + 'a' + 'a'
+    EXPECT_EQ("RSRF", processSequenceForward(&machine,
+        { kTrail, kTrail }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // [Trail] + [Trail] + [U] + | + 'a' + 'a'
+    EXPECT_EQ("RRRSRF", processSequenceForward(&machine,
+        { kTrail, kTrail, kRisU }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // [Trail] + [Trail] + [U] + [S] + | + 'a' + 'a'
+    EXPECT_EQ("RRRRRSRF", processSequenceForward(&machine,
+        { kTrail, kTrail, kRisU, kRisS }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + [Trail] + | + 'a' + 'a'
+    EXPECT_EQ("RSRF", processSequenceForward(&machine,
+        { kTrail }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // SOT + [Trail] + [U] + | + 'a' + 'a'
+    EXPECT_EQ("RRRSRF", processSequenceForward(&machine,
+        { kTrail, kRisU }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // SOT + [Trail] + [U] + [S] + | + 'a' + 'a'
+    EXPECT_EQ("RRRRRSRF", processSequenceForward(&machine,
+        { kTrail, kRisU, kRisS }, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, BrokenSurrogatePair)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+    // SOT + | + [Trail]
+    EXPECT_EQ("SF", processSequenceForward(&machine, kEmpty, { kTrail }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // SOT + | + [Lead] + 'a'
+    EXPECT_EQ("SRF", processSequenceForward(&machine, kEmpty, { kLead, 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // SOT + | + [Lead] + [Lead]
+    EXPECT_EQ("SRF", processSequenceForward(&machine, kEmpty,
+        { kLead, kLead }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+    // SOT + | + [Lead] + EOT
+    EXPECT_EQ("SR", processSequenceForward(&machine, kEmpty, { kLead }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, BreakImmediately_BMP)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + | + 'a' + 'a'
+    EXPECT_EQ("SRF", processSequenceForward(&machine, kEmpty, { 'a', 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + 'a' + U+1F441
+    EXPECT_EQ("SRRF", processSequenceForward(&machine, kEmpty, { 'a', kEye }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + 'a' + EOT
+    EXPECT_EQ("SR", processSequenceForward(&machine, kEmpty, { 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + 'a' + [Trail]
+    EXPECT_EQ("SRF", processSequenceForward(&machine, kEmpty, { 'a', kTrail }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + 'a' + [Lead] + 'a'
+    EXPECT_EQ("SRRF", processSequenceForward(&machine, kEmpty,
+        { 'a', kLead, 'a' }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + 'a' + [Lead] + [Lead]
+    EXPECT_EQ("SRRF", processSequenceForward(&machine, kEmpty,
+        { 'a', kLead, kLead }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + 'a' + [Lead] + EOT
+    EXPECT_EQ("SRR", processSequenceForward(&machine, kEmpty, { 'a', kLead }));
+    EXPECT_EQ(1, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, BreakImmediately_Supplementary)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + | + U+1F441 + 'a'
+    EXPECT_EQ("SRRF", processSequenceForward(&machine, kEmpty, { kEye, 'a' }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + U+1F441
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kEye }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + EOT
+    EXPECT_EQ("SRR", processSequenceForward(&machine, kEmpty, { kEye }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + [Trail]
+    EXPECT_EQ("SRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kTrail }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + [Lead] + 'a'
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kLead, 'a' }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + [Lead] + [Lead]
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kLead, kLead }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + [Lead] + EOT
+    EXPECT_EQ("SRRR", processSequenceForward(&machine, kEmpty,
+        { kEye, kLead }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, NotBreakImmediatelyAfter_BMP_BMP)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + | + U+231A + U+FE0F + 'a'
+    EXPECT_EQ("SRRF", processSequenceForward(&machine, kEmpty,
+        { kWatch, kVS16, 'a' }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+231A + U+FE0F + U+1F441
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kWatch, kVS16, kEye }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+231A + U+FE0F + EOT
+    EXPECT_EQ("SRR", processSequenceForward(&machine, kEmpty,
+        { kWatch, kVS16 }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+231A + U+FE0F + [Trail]
+    EXPECT_EQ("SRRF", processSequenceForward(&machine, kEmpty,
+        { kWatch, kVS16, kTrail }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+231A + U+FE0F + [Lead] + 'a'
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kWatch, kVS16, kLead, 'a' }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+231A + U+FE0F + [Lead] + [Lead]
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kWatch, kVS16, kLead, kLead }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+231A + U+FE0F + [Lead] + EOT
+    EXPECT_EQ("SRRR", processSequenceForward(&machine, kEmpty,
+        { kWatch, kVS16, kLead }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest,
+    NotBreakImmediatelyAfter_Supplementary_BMP)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + | + U+1F441 + U+FE0F + 'a'
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kVS16, 'a' }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + U+FE0F + U+1F441
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kVS16, kEye }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + U+FE0F + EOT
+    EXPECT_EQ("SRRR", processSequenceForward(&machine, kEmpty,
+        { kEye, kVS16 }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + U+FE0F + [Trail]
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kVS16, kTrail }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + U+FE0F + [Lead] + 'a'
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kVS16, kLead, 'a' }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + U+FE0F + [Lead] + [Lead]
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kEye, kVS16, kLead, kLead }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+1F441 + U+FE0F + [Lead] + EOT
+    EXPECT_EQ("SRRRR", processSequenceForward(&machine, kEmpty,
+        { kEye, kVS16, kLead }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest,
+    NotBreakImmediatelyAfter_BMP_Supplementary)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + | + U+845B + U+E0100 + 'a'
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanBMP, kVS17, 'a' }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+845B + U+E0100 + U+1F441
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanBMP, kVS17, kEye }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+845B + U+E0100 + EOT
+    EXPECT_EQ("SRRR", processSequenceForward(&machine, kEmpty,
+        { kHanBMP, kVS17 }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+845B + U+E0100 + [Trail]
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanBMP, kVS17, kTrail }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+845B + U+E0100 + [Lead] + 'a'
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanBMP, kVS17, kLead, 'a' }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+845B + U+E0100 + [Lead] + [Lead]
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanBMP, kVS17, kLead, kLead }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+845B + U+E0100 + [Lead] + EOT
+    EXPECT_EQ("SRRRR", processSequenceForward(&machine, kEmpty,
+        { kHanBMP, kVS17, kLead }));
+    EXPECT_EQ(3, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest,
+    NotBreakImmediatelyAfter_Supplementary_Supplementary)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + | + U+20000 + U+E0100 + 'a'
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanSIP, kVS17, 'a' }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+20000 + U+E0100 + U+1F441
+    EXPECT_EQ("SRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanSIP, kVS17, kEye }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+20000 + U+E0100 + EOT
+    EXPECT_EQ("SRRRR", processSequenceForward(&machine, kEmpty,
+        { kHanSIP, kVS17 }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+20000 + U+E0100 + [Trail]
+    EXPECT_EQ("SRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanSIP, kVS17, kTrail }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+20000 + U+E0100 + [Lead] + 'a'
+    EXPECT_EQ("SRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanSIP, kVS17, kLead, 'a' }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+20000 + U+E0100 + [Lead] + [Lead]
+    EXPECT_EQ("SRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kHanSIP, kVS17, kLead, kLead }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + U+20000 + U+E0100 + [Lead] + EOT
+    EXPECT_EQ("SRRRRR", processSequenceForward(&machine, kEmpty,
+        { kHanSIP, kVS17, kLead }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, MuchLongerCase)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    const UChar32 kMan = WTF::Unicode::manCharacter;
+    const UChar32 kZwj = WTF::Unicode::zeroWidthJoinerCharacter;
+    const UChar32 kHeart = WTF::Unicode::heavyBlackHeartCharacter;
+    const UChar32 kKiss = WTF::Unicode::kissMarkCharacter;
+
+    // U+1F468 U+200D U+2764 U+FE0F U+200D U+1F48B U+200D U+1F468 is a valid ZWJ
+    // emoji sequence.
+    // SOT + | + ZWJ Emoji Sequence + 'a'
+    EXPECT_EQ("SRRRRRRRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + ZWJ Emoji Sequence + U+1F441
+    EXPECT_EQ("SRRRRRRRRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, kEye }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + ZWJ Emoji Sequence + EOT
+    EXPECT_EQ("SRRRRRRRRRRR", processSequenceForward(&machine, kEmpty,
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + ZWJ Emoji Sequence + [Trail]
+    EXPECT_EQ("SRRRRRRRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, kTrail }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + ZWJ Emoji Sequence + [Lead] + 'a'
+    EXPECT_EQ("SRRRRRRRRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, kLead, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + ZWJ Emoji Sequence + [Lead] + [Lead]
+    EXPECT_EQ("SRRRRRRRRRRRRF", processSequenceForward(&machine, kEmpty,
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, kLead, kLead }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("SRRRRRRRRRRRR", processSequenceForward(&machine, kEmpty,
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, kLead }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // Preceding text should not affect the result except for flags.
+    // 'a' + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("SRRRRRRRRRRRF", processSequenceForward(&machine,
+        { 'a' },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // U+1F441 + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("RSRRRRRRRRRRRF", processSequenceForward(&machine,
+        { kEye },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // [Lead] + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("SRRRRRRRRRRRF", processSequenceForward(&machine,
+        { kLead },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [Trail] + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("RSRRRRRRRRRRRF", processSequenceForward(&machine,
+        { 'a', kTrail },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // [Trail] + [Trail] + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("RSRRRRRRRRRRRF", processSequenceForward(&machine,
+        { kTrail, kTrail },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + [Trail] + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("RSRRRRRRRRRRRF", processSequenceForward(&machine,
+        { kTrail },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [U] + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("RRSRRRRRRRRRRRF", processSequenceForward(&machine,
+        { 'a', kRisU },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [U] + [S] + | + ZWJ Emoji Sequence + [Lead] + EOT
+    EXPECT_EQ("RRRRSRRRRRRRRRRRF", processSequenceForward(&machine,
+        { 'a', kRisU, kRisS },
+        { kMan, kZwj, kHeart, kVS16, kZwj, kKiss, kZwj, kMan, 'a' }));
+    EXPECT_EQ(11, machine.finalizeAndGetBoundaryOffset());
+
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, singleFlags)
+{
+    const std::vector<UChar32> kEmpty;
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + | + [U] + [S]
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine,
+        kEmpty, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + | + [U] + [S]
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine,
+        { 'a' }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // U+1F441 + | + [U] + [S]
+    EXPECT_EQ("RSRRRF", processSequenceForward(&machine,
+        { kEye }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // [Lead] + | + [U] + [S]
+    EXPECT_EQ("SRRRF", processSequenceForward(&machine,
+        { kLead }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [Trail] + | + [U] + [S]
+    EXPECT_EQ("RSRRRF", processSequenceForward(&machine,
+        { 'a', kTrail }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // [Trail] + [Trail] + | + [U] + [S]
+    EXPECT_EQ("RSRRRF", processSequenceForward(&machine,
+        { kTrail, kTrail }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + [Trail] + | + [U] + [S]
+    EXPECT_EQ("RSRRRF", processSequenceForward(&machine,
+        { kTrail }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, twoFlags)
+{
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + [U] + [S] + | + [U] + [S]
+    EXPECT_EQ("RRRRSRRRF", processSequenceForward(&machine,
+        { kRisU, kRisS }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [U] + [S] + | + [U] + [S]
+    EXPECT_EQ("RRRRSRRRF", processSequenceForward(&machine,
+        { 'a', kRisU, kRisS }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // U+1F441 + [U] + [S] + | + [U] + [S]
+    EXPECT_EQ("RRRRRSRRRF", processSequenceForward(&machine,
+        { kEye, kRisU, kRisS }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // [Lead] + [U] + [S] + | + [U] + [S]
+    EXPECT_EQ("RRRRSRRRF", processSequenceForward(&machine,
+        { kLead, kRisU, kRisS }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [Trail] + [U] + [S] + | + [U] + [S]
+    EXPECT_EQ("RRRRRSRRRF", processSequenceForward(&machine,
+        { 'a', kTrail, kRisU, kRisS }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // [Trail] + [Trail] + [U] + [S] + | + [U] + [S]
+    EXPECT_EQ("RRRRRSRRRF", processSequenceForward(&machine,
+        { kTrail, kTrail, kRisU, kRisS }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + [Trail] + [U] + [S] + | + [U] + [S]
+    EXPECT_EQ("RRRRRSRRRF", processSequenceForward(&machine,
+        { kTrail, kRisU, kRisS }, { kRisU, kRisS }));
+    EXPECT_EQ(4, machine.finalizeAndGetBoundaryOffset());
+}
+
+TEST(ForwardGraphemeBoundaryStatemachineTest, oddNumberedFlags)
+{
+    ForwardGraphemeBoundaryStateMachine machine;
+
+    // SOT + [U] + | + [S] + [S]
+    EXPECT_EQ("RRSRRRF", processSequenceForward(&machine,
+        { kRisU }, { kRisS, kRisU }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [U] + | + [S] + [S]
+    EXPECT_EQ("RRSRRRF", processSequenceForward(&machine,
+        { 'a', kRisU }, { kRisS, kRisU }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // U+1F441 + [U] + | + [S] + [S]
+    EXPECT_EQ("RRRSRRRF", processSequenceForward(&machine,
+        { kEye, kRisU }, { kRisS, kRisU }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // [Lead] + [U] + | + [S] + [S]
+    EXPECT_EQ("RRSRRRF", processSequenceForward(&machine,
+        { kLead, kRisU }, { kRisS, kRisU }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // 'a' + [Trail] + [U] + | + [S] + [S]
+    EXPECT_EQ("RRRSRRRF", processSequenceForward(&machine,
+        { 'a', kTrail, kRisU }, { kRisS, kRisU }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // [Trail] + [Trail] + [U] + | + [S] + [S]
+    EXPECT_EQ("RRRSRRRF", processSequenceForward(&machine,
+        { kTrail, kTrail, kRisU }, { kRisS, kRisU }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+
+    // SOT + [Trail] + [U] + | + [S] + [S]
+    EXPECT_EQ("RRRSRRRF", processSequenceForward(&machine,
+        { kTrail, kRisU }, { kRisS, kRisU }));
+    EXPECT_EQ(2, machine.finalizeAndGetBoundaryOffset());
+}
+
+} // namespace blink