/myProject
  /src
    /main
      /java
        /com.lexcorp
          /core
            /email
              /providers
                emailProvider.java

/myProjectTests
  /src
    /main
      /java
        /com.lexcorp.core.email.providers
          emailProviderTest.java

package com.lexcorp.core.email.providers;

import junit.framework.TestCase;
import org.junit.Test;

public class EmailProviderTest extends TestCase {

    private final String username = "[testAccount]";

    private final String password = "[testPassword]";

    @Test
    public void thisAlwaysPasses() {
        assertTrue(true);
    }
}

junit.framework.AssertionFailedError: No tests found in com.lexcorp.core.email.providers.EmailProviderTest
    at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
    at org.junit.runners.Suite.runChild(Suite.java:127)
    at org.junit.runners.Suite.runChild(Suite.java:26)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:202)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:65)
    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:120)

defaultConfig {
    ...
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}

public class EmailProviderTest {

@Test
public void method1(){
    // Do some stuff...
}

@Test
public void testMethod1(){
    // Do some stuff...
}

@DataProvider
public static Object[][] invalidAdjustment() {
    return new Object[][]{
            {"some n text", false},
            };
}