java.lang.Exception: Custom runner class AndroidJUnit4 should have a public constructor with signature AndroidJUnit4(Class testClass)

gradle looks like:

apply plugin: 'com.android.application'  android {     compileSdkVersion 25     buildToolsVersion "25.0.2"      defaultConfig {         applicationId "com.google.developer.taskmaker"         minSdkVersion 19         targetSdkVersion 25         versionCode 1         versionName "1.0"          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"     }     buildTypes {         release {             minifyEnabled false             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'         }     } }  configurations.all {     resolutionStrategy {         force 'com.android.support:support-annotations:25.2.0'     } }   dependencies {     compile fileTree(dir: 'libs', include: ['*.jar'])     testCompile 'junit:junit:4.12'     compile 'com.android.support:appcompat-v7:25.2.0'     compile 'com.android.support:recyclerview-v7:25.2.0'     compile 'com.android.support:design:25.2.0'     compile 'com.android.support:preference-v7:25.2.0'     debugCompile 'im.dino:dbinspector:3.4.1@aar'     // Android JUnit Runner     compile 'com.google.android.gms:play-services-appindexing:8.4.0'     // Android runner and rules support      // add this for intent mocking support     androidTestCompile 'com.android.support.test.espresso:espresso-intents:2.2.2'      // add this for webview testing support     androidTestCompile 'com.android.support.test.espresso:espresso-web:2.2.2'     compile 'com.android.support.test:runner:0.5'     compile 'com.android.support.test:rules:0.5'     compile 'com.android.support.test.espresso:espresso-core:2.2.2' } 

Unit test case looks like

@RunWith(AndroidJUnit4.class) public class TestClass {      @Rule     public ActivityTestRule<MainActivity> mActivityRule =             new ActivityTestRule<>(MainActivity.class);      @Test     public void buttonClick(){         onView(withId(R.id.fab)).perform(click()).check(matches(isDisplayed()));     }  } 

Error message looks like:

java.lang.Exception: Custom runner class AndroidJUnit4 should have a public constructor with signature AndroidJUnit4(Class testClass)      at org.junit.runners.model.InitializationError.<init>(InitializationError.java:38)     at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:111)     at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:86)     at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)     at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)     at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)     at org.junit.runners.model.RunnerBuilder.runners(RunnerBuilder.java:101)     at org.junit.runners.model.RunnerBuilder.runners(RunnerBuilder.java:87)     at com.intellij.junit4.JUnit46ClassesRequestBuilder.collectWrappedRunners(JUnit46ClassesRequestBuilder.java:90)     at com.intellij.junit4.JUnit46ClassesRequestBuilder.getClassesRequest(JUnit46ClassesRequestBuilder.java:51)     at com.intellij.junit4.JUnit4TestRunnerUtil.buildRequest(JUnit4TestRunnerUtil.java:91)     at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:95)     at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)     at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)     at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)     at java.lang.reflect.Method.invoke(Method.java:497)     at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)   Process finished with exit code -1 

I have already check other answers but not getting solution.Please tell where thing goes wrong. When running this code I am getting error

3 Answers

Answers 1

I had the same problem. I'm working in Android studio 2.3.1. I checked my run configurations. Under Run->Edit Configurations and discovered the test I was trying to run as an instrumented test was under the Android JUnit tests category, even though I had it in the androidTest directory in my project. I added an Android Instrumented Test (hit the plus button in the corner) and set it to point to the test I was trying to run. That fixed it for me.

Answers 2

This error can be replicated by making a new Application with the default template in Android Studio and copying the auto-generated ExampleInstrumentedTest from the androidTest folder to the test folder:

Here's what the error looks like:

Note that in order to replicate the problem you would also have to incorrectly add dependencies to the module-level build.gradle:

Explanation:

There are two types of unit tests in Android:

1. Instrumented tests
2. Local unit tests

Instrumented tests

Instrumented tests are tests that are designed to run on a handset or emulator. These are tests where you need access to a fully-functional part of the Android library (like a real Context for example). These need to go in the androidTest folder and dependencies for these tests (e.g., Espresso, com.android.support.test.rules:0.5) will be prefixed with androidTestCompile in your build.gradle.

Here is an example instrumented test:

import android.content.Context; import android.support.test.InstrumentationRegistry; import android.support.test.runner.AndroidJUnit4;  import org.junit.Test; import org.junit.runner.RunWith;  import static org.junit.Assert.assertEquals;  /**  * Instrumentation test, which will execute on an Android device.  *  * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>  */ @RunWith(AndroidJUnit4.class) public class ExampleInstrumentedTest {     @Test     public void useAppContext() throws Exception {         // Context of the app under test.         Context appContext = InstrumentationRegistry.getTargetContext();          assertEquals("com.gyaltsab.myapplication", appContext.getPackageName());     } } 

Local unit tests

Local unit tests are tests that you can run in your IDE. They normally don't depend on any part of the Android library not available on a standard JVM (e.g., they won't depend on Context). The dependencies for these go in the testCompile part of your build.gradle.

Here is an example unit test:

import org.junit.Test;  import static org.junit.Assert.*;  /**  * Example local unit test, which will execute on the development machine (host).  *  * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>  */ public class ExampleUnitTest {     @Test     public void addition_isCorrect() throws Exception {         assertEquals(4, 2 + 2);     } } 

Please see the official docs for a more complete explanation.

Answers 3

Try moving your test file to the androidTest folder.

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