我的 build.gradle 是这样的

apply plugin: 'com.android.application'

android {
compileSdkVersion 25
buildToolsVersion "25.0.3"
defaultConfig {
applicationId "com.example.administrator.myapplication"
minSdkVersion 15
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'
}
}
}

dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:25.3.1'
compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha7'
testCompile 'junit:junit:4.12'
compile files('libs/uiautomator.jar')
}

您好，我出现这样的问题弄了好久都没办法解决，请问能帮我看看吗？谢谢
junit.framework.AssertionFailedError: Exception in constructor: testDemo (java.lang.RuntimeException: Stub!
at com.android.uiautomator.testrunner.UiAutomatorTestCase.(UiAutomatorTestCase.java:5)
at com.example.administrator.myapplication.TestCalculator.(TestCalculator.java:10)
at java.lang.reflect.Constructor.newInstance0(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:430)
at junit.framework.TestSuite.createTest(TestSuite.java:61)
at junit.framework.TestSuite.addTestMethod(TestSuite.java:294)
at junit.framework.TestSuite.addTestsFromTestCase(TestSuite.java:150)
at junit.framework.TestSuite.(TestSuite.java:129)
at android.support.test.internal.runner.junit3.NonLeakyTestSuite.(NonLeakyTestSuite.java:34)
at android.support.test.internal.runner.junit3.AndroidTestSuite.(AndroidTestSuite.java:49)
at android.support.test.internal.runner.junit3.AndroidJUnit3Builder.runnerForClass(AndroidJUnit3Builder.java:52)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
at org.junit.runner.Computer.getRunner(Computer.java:40)
at org.junit.runner.Computer$1.runnerForClass(Computer.java:31)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
at org.junit.runners.model.RunnerBuilder.runners(RunnerBuilder.java:101)
at org.junit.runners.model.RunnerBuilder.runners(RunnerBuilder.java:87)
at org.junit.runners.Suite.(Suite.java:81)
at org.junit.runner.Computer.getSuite(Computer.java:28)
at android.support.test.internal.runner.TestRequestBuilder.classes(TestRequestBuilder.java:789)
at android.support.test.internal.runner.TestRequestBuilder.build(TestRequestBuilder.java:753)
at android.support.test.runner.AndroidJUnitRunner.buildRequest(AndroidJUnitRunner.java:354)
at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:260)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1932)
)
at junit.framework.Assert.fail(Assert.java:50)
at junit.framework.TestSuite$1.runTest(TestSuite.java:97)
at junit.framework.TestCase.runBare(TestCase.java:134)
at junit.framework.TestResult$1.protect(TestResult.java:115)
at android.support.test.internal.runner.junit3.AndroidTestResult.runProtected(AndroidTestResult.java:77)
at junit.framework.TestResult.run(TestResult.java:118)
at android.support.test.internal.runner.junit3.AndroidTestResult.run(AndroidTestResult.java:55)
at junit.framework.TestCase.run(TestCase.java:124)
at android.support.test.internal.runner.junit3.NonLeakyTestSuite$NonLeakyTest.run(NonLeakyTestSuite.java:63)
at junit.framework.TestSuite.runTest(TestSuite.java:243)
at junit.framework.TestSuite.run(TestSuite.java:238)
at android.support.test.internal.runner.junit3.DelegatingTestSuite.run(DelegatingTestSuite.java:103)
at android.support.test.internal.runner.junit3.AndroidTestSuite.run(AndroidTestSuite.java:69)
at android.support.test.internal.runner.junit3.JUnit38ClassRunner.run(JUnit38ClassRunner.java:103)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:27)
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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at android.support.test.internal.runner.TestExecutor.execute(TestExecutor.java:59)
at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:262)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1932)

Tests ran to completion.

也是报了这个问题 junit.framework.AssertionFailedError: Exception in constructor: testDemo (java.lang.RuntimeException: Stub!

您好，你遇到的问题解决了吗？我遇到了和你一样的问题，可以帮忙解决一下吗？