third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetectorTest.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/paint/FirstMeaningfulPaintDetector.h"

#include "core/paint/PaintTiming.h"
#include "core/testing/DummyPageHolder.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace blink {

class FirstMeaningfulPaintDetectorTest : public testing::Test {
protected:
    void SetUp() override
    {
        m_dummyPageHolder = DummyPageHolder::create(IntSize(800, 600));
        s_timeElapsed = 0.0;
        m_originalTimeFunction = setTimeFunctionsForTesting(returnMockTime);
    }

    void TearDown() override
    {
        setTimeFunctionsForTesting(m_originalTimeFunction);
    }

    Document& document() { return m_dummyPageHolder->document(); }
    PaintTiming& paintTiming() { return PaintTiming::from(document()); }
    FirstMeaningfulPaintDetector& detector() { return paintTiming().firstMeaningfulPaintDetector(); }

    void simulateLayoutAndPaint(int newElements)
    {
        StringBuilder builder;
        for (int i = 0; i < newElements; i++)
            builder.append("<span>a</span>");
        document().write(builder.toString());
        document().updateStyleAndLayout();
        detector().notifyPaint();
    }

    void simulateNetworkStable()
    {
        detector().networkStableTimerFired(nullptr);
    }

private:
    static double returnMockTime()
    {
        s_timeElapsed += 1.0;
        return s_timeElapsed;
    }

    std::unique_ptr<DummyPageHolder> m_dummyPageHolder;
    TimeFunction m_originalTimeFunction;
    static double s_timeElapsed;
};

double FirstMeaningfulPaintDetectorTest::s_timeElapsed;

TEST_F(FirstMeaningfulPaintDetectorTest, NoFirstPaint)
{
    simulateLayoutAndPaint(1);
    simulateNetworkStable();
    EXPECT_EQ(paintTiming().firstMeaningfulPaint(), 0.0);
}

TEST_F(FirstMeaningfulPaintDetectorTest, OneLayout)
{
    paintTiming().markFirstPaint();
    simulateLayoutAndPaint(1);
    double afterPaint = monotonicallyIncreasingTime();
    EXPECT_EQ(paintTiming().firstMeaningfulPaint(), 0.0);
    simulateNetworkStable();
    EXPECT_GT(paintTiming().firstMeaningfulPaint(), paintTiming().firstPaint());
    EXPECT_LT(paintTiming().firstMeaningfulPaint(), afterPaint);
}

TEST_F(FirstMeaningfulPaintDetectorTest, TwoLayoutsSignificantSecond)
{
    paintTiming().markFirstPaint();
    simulateLayoutAndPaint(1);
    double afterLayout1 = monotonicallyIncreasingTime();
    simulateLayoutAndPaint(10);
    double afterLayout2 = monotonicallyIncreasingTime();
    simulateNetworkStable();
    EXPECT_GT(paintTiming().firstMeaningfulPaint(), afterLayout1);
    EXPECT_LT(paintTiming().firstMeaningfulPaint(), afterLayout2);
}

TEST_F(FirstMeaningfulPaintDetectorTest, TwoLayoutsSignificantFirst)
{
    paintTiming().markFirstPaint();
    simulateLayoutAndPaint(10);
    double afterLayout1 = monotonicallyIncreasingTime();
    simulateLayoutAndPaint(1);
    simulateNetworkStable();
    EXPECT_GT(paintTiming().firstMeaningfulPaint(), paintTiming().firstPaint());
    EXPECT_LT(paintTiming().firstMeaningfulPaint(), afterLayout1);
}

} // namespace blink