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Unit Test

unit-test/README.md

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Unit Test

This Android sample shows how to write unit tests for native code with googletest, and run them on-device.

Writing unit tests

This app has a very simple library containing a function to add two numbers.

adder.h:

C++
#pragma once

int add(int a, int b);

adder.cpp:

C++
#include "adder.h"

int add(int a, int b) { return a + b; }

adder_test.cpp contains a unit test for this function:

C++
#include "adder.h"

#include "gtest/gtest.h"

TEST(adder, adder) { EXPECT_EQ(3, add(1, 2)); }

Building and running the tests

We need to add a library for the test to CMakeLists.txt, which depends on googletest and junit-gtest:

cmake
find_package(googletest REQUIRED CONFIG)
find_package(junit-gtest REQUIRED CONFIG)
cmake
add_library(app_tests SHARED adder_test.cpp)
target_link_libraries(app_tests
  PRIVATE
    $<TARGET_OBJECTS:adder>
    googletest::gtest
    junit-gtest::junit-gtest
)

We need to add googletest and junit-gtest as dependencies in app/build.gradle. Googletest uses prefab, so we enable that.

    build_features {
    	prefab true
    }

dependencies {
    implementation 'androidx.test.ext:junit-gtest:1.0.0-alpha01'
    implementation 'com.android.ndk.thirdparty:googletest:1.11.0-beta-1'
}

Finally, we need a wrapper in androidTest, NativeTests.kt:

kotlin
package com.example.unittest

import androidx.test.ext.junitgtest.GtestRunner
import androidx.test.ext.junitgtest.TargetLibrary
import org.junit.runner.RunWith

@RunWith(GtestRunner::class)
@TargetLibrary(libraryName = "app_tests")
class NativeTests

You can run the test on a phone or emulator as described in the Android developer documentation.

Try deliberately breaking the test, like this:

C++
EXPECT_EQ(4, add(1, 2));

You should see a failure message like this:

java.lang.AssertionError:
/path/to/ndk-samples/unit-test/app/src/main/cpp/adder_test.cpp:6
Expected equality of these values:
4
add(1,2)
Which is: 3

Screenshot