How to mock method e in Log

问题:

Here Utils.java is my class to be tested and following is the method which is called in UtilsTest class. Even if I am mocking Log.e method as shown below

 @Before
  public void setUp() {
  when(Log.e(any(String.class),any(String.class))).thenReturn(any(Integer.class));
            utils = spy(new Utils());
  }

I am getting the following exception

java.lang.RuntimeException: Method e in android.util.Log not mocked. See http://g.co/androidstudio/not-mocked for details.
    at android.util.Log.e(Log.java)
    at com.xxx.demo.utils.UtilsTest.setUp(UtilsTest.java:41)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:78)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:212)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:68)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)

回答1:

This worked out for me. I'm only using JUnit and I was able to mock up the Log class without any third party lib very easy. Just create a file Log.java inside app/src/test/java/android/util with contents:

public class Log {
    public static int d(String tag, String msg) {
        System.out.println("DEBUG: " + tag + ": " + msg);
        return 0;
    }

    public static int i(String tag, String msg) {
        System.out.println("INFO: " + tag + ": " + msg);
        return 0;
    }

    public static int w(String tag, String msg) {
        System.out.println("WARN: " + tag + ": " + msg);
        return 0;
    }

    public static int e(String tag, String msg) {
        System.out.println("ERROR: " + tag + ": " + msg);
        return 0;
    }

    // add other methods if required...
}

回答2:

You can put this into your gradle script:

android {
   ...
   testOptions { 
       unitTests.returnDefaultValues = true
   }
}

That will decide whether unmocked methods from android.jar should throw exceptions or return default values.

回答3:

Using PowerMockito:

@RunWith(PowerMockRunner.class)
@PrepareForTest({Log.class})
public class TestsToRun() {
    @Test
    public void test() {
        PowerMockito.mockStatic(Log.class);
    }
}

And you're good to go. Be advised that PowerMockito will not automatically mock inherited static methods, so if you want to mock a custom logging class that extends Log, you must still mock Log for calls such as MyCustomLog.e().

回答4:

Use PowerMockito.

@RunWith(PowerMockRunner.class)
@PrepareForTest({ClassNameOnWhichTestsAreWritten.class , Log.class})
public class TestsOnClass() {
    @Before
    public void setup() {
        PowerMockito.mockStatic(Log.class);
    }
    @Test
    public void Test_1(){

    }
    @Test
    public void Test_2(){

    }
 }

回答5:

Mockito doesn't mock static methods. Use PowerMockito on top. Here is an example.

回答6:

Using PowerMock one can mock Log.i/e/w static methods from Android logger. Of course ideally you should create a logging interface or a facade and provide a way of logging to different sources.

This is a complete solution in Kotlin:

import org.powermock.modules.junit4.PowerMockRunner
import org.powermock.api.mockito.PowerMockito
import org.powermock.core.classloader.annotations.PrepareForTest

/**
 * Logger Unit tests
 */
@RunWith(PowerMockRunner::class)
@PrepareForTest(Log::class)
class McLogTest {

    @Before
    fun beforeTest() {
        PowerMockito.mockStatic(Log::class.java)
        Mockito.`when`(Log.i(any(), any())).then {
            println(it.arguments[1] as String)
            1
        }
    }

    @Test
    fun logInfo() {
        Log.i("TAG1,", "This is a samle info log content -> 123")
    }
}

remember to add dependencies in gradle:

dependencies {
    testImplementation "junit:junit:4.12"
    testImplementation "org.mockito:mockito-core:2.15.0"
    testImplementation "io.kotlintest:kotlintest:2.0.7"
    testImplementation 'org.powermock:powermock-module-junit4-rule:2.0.0-beta.5'
    testImplementation 'org.powermock:powermock-core:2.0.0-beta.5'
    testImplementation 'org.powermock:powermock-module-junit4:2.0.0-beta.5'
    testImplementation 'org.powermock:powermock-api-mockito2:2.0.0-beta.5'
}

To mock Log.println method use:

Mockito.`when`(Log.println(anyInt(), any(), any())).then {
    println(it.arguments[2] as String)
    1
}

回答7:

I would recommend using timber for your logging.

Though it will not log anything when running tests but it doesn't fail your tests unnecessarily the way android Log class does. Timber gives you a lot of convenient control over both debug and production build of you app.

回答8:

Another solution is to use Robolectric. If you want to try it, check its setup.

In your module's build.gradle, add the following

testImplementation "org.robolectric:robolectric:3.8"

android {
  testOptions {
    unitTests {
      includeAndroidResources = true
    }
  }
}

And in your test class,

@RunWith(RobolectricTestRunner.class)
public class SandwichTest {
  @Before
  public void setUp() {
  }
}