Google Test and Mock example

main.cpp

// To Build and Run
// g++ main.cpp -g -lgtest -lgmock
// ./a.out
// links
// https://github.com/google/googletest/blob/main/docs/gmock_cook_book.md
// https://stackoverflow.com/questions/58501850/googlemock-how-to-use-mocking-in-test
// https://qiangbo-workspace.oss-cn-shanghai.aliyuncs.com/2018-12-05-gtest-and-coverage/PlainGoogleQuickTestReferenceGuide1.pdf

#include "gtest/gtest.h"
#include "gmock/gmock.h"

using ::testing::_;
using ::testing::AtLeast;
using ::testing::Return;

class IUniverse
{
public:
    virtual ~IUniverse() = default;
    virtual bool makeEarth() = 0;
    virtual std::string getWeather() = 0;
    virtual float cultivateSoil(double mineralCount, int treeCount, float waterCubics) = 0;
};

class Universe : public IUniverse
{
public:
    ~Universe() override {}

    bool makeEarth() override
    {
        throw std::runtime_error("Not Enough Powers");
        return false;
    }

    std::string getWeather() override
    {
        throw std::runtime_error("Its gettin hot in here");
    }

    float cultivateSoil(double mineralCount, int treeCount, float waterCubics) override
    {
        auto cultivationPercentage = ((float)(mineralCount * treeCount * waterCubics) / 0);
        return cultivationPercentage;
    }
};

class MockUniverse : public IUniverse
{
public:
    ~MockUniverse() override {}
    MOCK_METHOD(bool, makeEarth, (), (override));
    MOCK_METHOD(std::string, getWeather, (), (override));
    MOCK_METHOD(float, cultivateSoil, (double, int, float), (override));
};

class Human
{
public:
    IUniverse &universe;
    Human(IUniverse &newUniverse) : universe{newUniverse} {}

    bool tweakPlanet()
    {
        std::string s = universe.getWeather();
        return true;
    }

};

TEST(Universe, makeEarth)
{
    MockUniverse universe;

    EXPECT_CALL(universe, makeEarth()) // #3
        .WillOnce(Return(false))
        .WillRepeatedly(Return(true));

    EXPECT_FALSE(universe.makeEarth());
    EXPECT_TRUE(universe.makeEarth()); // #5
}

TEST(Universe, getWeather)
{
    MockUniverse universe;

    EXPECT_CALL(universe, getWeather()) // #3
        .WillOnce(Return("Summer"))
        .WillOnce(Return("Winter"))
        .WillOnce(Return("Spring"))
        .WillOnce(Return("Autumn"))
        .WillRepeatedly(Return("Raining"));

    EXPECT_EQ(universe.getWeather(), "Summer");
    EXPECT_EQ(universe.getWeather(), "Winter");
    EXPECT_EQ(universe.getWeather(), "Spring");
    EXPECT_EQ(universe.getWeather(), "Autumn");
    EXPECT_EQ(universe.getWeather(), "Raining");
}

TEST(Universe, cultivateSoil)
{
    MockUniverse universe;

    EXPECT_CALL(universe, cultivateSoil(_, _, _)) // #3
        .WillOnce(Return(98.4234))
        .WillRepeatedly(Return(1.99999));

    ASSERT_FLOAT_EQ(universe.cultivateSoil(10.0, 0, 0), 98.4234);
    ASSERT_FLOAT_EQ(universe.cultivateSoil(10.0, 0, 0), 1.99999);
    ASSERT_FLOAT_EQ(universe.cultivateSoil(0, 0, 0), 1.99999);
}

TEST(Universe, humanMakesEarth)
{
    MockUniverse mUniverse;

    Human human(mUniverse);
    EXPECT_CALL(mUniverse, makeEarth()) // #3
        .WillOnce(Return(false))
        .WillRepeatedly(Return(true));

    EXPECT_FALSE(human.universe.makeEarth());
    EXPECT_TRUE(human.universe.makeEarth()); // #5
}

TEST(Universe, humanGetsWeather)
{
    MockUniverse mUniverse;

    Human human(mUniverse);
    EXPECT_CALL(mUniverse, getWeather()) 
        .WillOnce(Return("Summer"))
        .WillRepeatedly(Return("Raining"));

    EXPECT_EQ(mUniverse.getWeather(), "Summer");
    EXPECT_NE(mUniverse.getWeather(), "Winter");
    EXPECT_EQ(mUniverse.getWeather(), "Raining");
    EXPECT_EQ(mUniverse.getWeather(), "Raining");
}

int main(int argc, char **argv)
{
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}