How to use printHeader method of junit.textui.ResultPrinter class

Hope you have spring-boot-starter-web dependency. Not sure which version of Spring boot you use, but build mockMvc this way instead?

@RunWith(SpringRunner.class)
@SpringBootTest
public class ApplicationTest {

  @Autowired
  private WebApplicationContext webApplicationContext;
  private MockMvc mockMvc;

  @Before
  public void setUp() {
    mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext).build();
  }

The easiest (as in least amount of new code required) way to do this is to run the test as a parametrized test (annotate with an @RunWith(Parameterized.class) and add a method to provide 10 empty parameters). That way the framework will run the test 10 times.

This test would need to be the only test in the class, or better put all test methods should need to be run 10 times in the class.

Here is an example:

@RunWith(Parameterized.class)
public class RunTenTimes {

    @Parameterized.Parameters
    public static Object[][] data() {
        return new Object[10][0];
    }

    public RunTenTimes() {
    }

    @Test
    public void runsTenTimes() {
        System.out.println("run");
    }
}

With the above, it is possible to even do it with a parameter-less constructor, but I'm not sure if the framework authors intended that, or if that will break in the future.

If you are implementing your own runner, then you could have the runner run the test 10 times. If you are using a third party runner, then with 4.7, you can use the new @Rule annotation and implement the MethodRule interface so that it takes the statement and executes it 10 times in a for loop. The current disadvantage of this approach is that @Before and @After get run only once. This will likely change in the next version of JUnit (the @Before will run after the @Rule), but regardless you will be acting on the same instance of the object (something that isn't true of the Parameterized runner). This assumes that whatever runner you are running the class with correctly recognizes the @Rule annotations. That is only the case if it is delegating to the JUnit runners.

If you are running with a custom runner that does not recognize the @Rule annotation, then you are really stuck with having to write your own runner that delegates appropriately to that Runner and runs it 10 times.

Note that there are other ways to potentially solve this (such as the Theories runner) but they all require a runner. Unfortunately JUnit does not currently support layers of runners. That is a runner that chains other runners.

There's no big advantage for those cases where an assertFoo exists that exactly matches your intent. In those cases they behave almost the same.

But when you come to checks that are somewhat more complex, then the advantage becomes more visible:

val foo = List.of("someValue");
assertTrue(foo.contains("someValue") && foo.contains("anotherValue"));

Expected: is <true>
         but: was <false>

vs.

val foo = List.of("someValue");
assertThat(foo, containsInAnyOrder("someValue", "anotherValue"));

Expected: iterable with items ["someValue", "anotherValue"] in any order
     but: no item matches: "anotherValue" in ["someValue"]

One can discuss which one of those is easier to read, but once the assert fails, you'll get a good error message from assertThat, but only a very minimal amount of information from assertTrue.

You cannot do this because according to spec you cannot put the same annotation twice on the same annotated element.

So, what is the solution? The solution is to put only one @RunWith() with runner you cannot stand without and replace other one with something else. In your case I guess you will remove MockitoJUnitRunner and do programatically what it does.

In fact the only thing it does it runs:

MockitoAnnotations.initMocks(test);

in the beginning of test case. So, the simplest solution is to put this code into setUp() method:

@Before
public void setUp() {
    MockitoAnnotations.initMocks(this);
}

I am not sure, but probably you should avoid multiple call of this method using flag:

private boolean mockInitialized = false;
@Before
public void setUp() {
    if (!mockInitialized) {
        MockitoAnnotations.initMocks(this);
        mockInitialized = true;  
    }
}

However better, reusable solution may be implemented with JUnt's rules.

public class MockitoRule extends TestWatcher {
    private boolean mockInitialized = false;

    @Override
    protected void starting(Description d) {
        if (!mockInitialized) {
            MockitoAnnotations.initMocks(this);
            mockInitialized = true;  
        }
    }
}

Now just add the following line to your test class:

@Rule public MockitoRule mockitoRule = MockitoJUnit.rule();

and you can run this test case with any runner you want.

You shouldn't override your <sourceDirectory> setting in the POM's <build> element unless you have a good reason to. This attribute determines where Maven looks for non-test code. The default value for this attribute is src/main/java. The <testSourceDirectory> attribute sets the path to test code (this defaults to src/test/java. By setting the <sourceDirectory> to simply src, Maven considers that entire directory to contain main application code. Since the src directory contains src/test/java, Maven then tries to compile your test code as part of the main application.

This is significant because when compiling the main application (during the compile phase), Maven omits dependencies with test scope. Test code is compiled in a separate phase (the test-compile phase) after the main compile.

So since Maven tried to compile your test code as part of the main application, it omitted the junit dependency, and they weren't available on the classpath. The solution here is to simply not specify the <sourceDirectory> element in the POM.

Update 2015/10

It is now possible via the AndroidJUnitRunner, which is part of the Android Testing Support Library. In short, you need to do the following in a Gradle-based project:

1. Add the dependencies:

   dependencies {
       compile 'com.android.support:support-annotations:22.2.0'
       androidTestCompile 'com.android.support.test:runner:0.4.1'
   }
   

2. Specify the testInstrumentationRunner:

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

3. Annotate your test class with @RunWith(AndroidJUnit4.class).

4. Write your tests in normal JUnit4 style.

Also see the Espresso setup instructions. Note that you don't need Espresso itself for plain JUnit4 tests.

Why it's needed

There are very little information I could find on the internet on this topic. The best I found was the info on InstrumentationTestRunner.

There are nothing preventing JUnit4 tests from running on an Android device just like any other Java code. However, the Android test framework does some additional work:

1. It sends test results back to your development machine over ADB.
2. It does instrumentation (I'm not sure what exactly this involves).

The above is performed by some extensions specifically for JUnit3.

This JUnit3-specific code seems to be part of the InstrumentationTestRunner which forms part of the core Android system. However, as is evident with AndroidJUnitRunner, it is possible to use a custom test runner that supports JUnit4 or other frameworks.

You can try @Rule annotation. Here is the example from the docs:

public static class UsesExternalResource {
    Server myServer = new Server();

    @Rule public ExternalResource resource = new ExternalResource() {
        @Override
        protected void before() throws Throwable {
            myServer.connect();
        };

        @Override
        protected void after() {
            myServer.disconnect();
        };
    };

    @Test public void testFoo() {
        new Client().run(myServer);
    }
}

You just need to create FileResource class extending ExternalResource.

Full Example

import static org.junit.Assert.*;

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ExternalResource;

public class TestSomething
{
    @Rule
    public ResourceFile res = new ResourceFile("/res.txt");

    @Test
    public void test() throws Exception
    {
        assertTrue(res.getContent().length() > 0);
        assertTrue(res.getFile().exists());
    }
}

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;

import org.junit.rules.ExternalResource;

public class ResourceFile extends ExternalResource
{
    String res;
    File file = null;
    InputStream stream;

    public ResourceFile(String res)
    {
        this.res = res;
    }

    public File getFile() throws IOException
    {
        if (file == null)
        {
            createFile();
        }
        return file;
    }

    public InputStream getInputStream()
    {
        return stream;
    }

    public InputStream createInputStream()
    {
        return getClass().getResourceAsStream(res);
    }

    public String getContent() throws IOException
    {
        return getContent("utf-8");
    }

    public String getContent(String charSet) throws IOException
    {
        InputStreamReader reader = new InputStreamReader(createInputStream(),
            Charset.forName(charSet));
        char[] tmp = new char[4096];
        StringBuilder b = new StringBuilder();
        try
        {
            while (true)
            {
                int len = reader.read(tmp);
                if (len < 0)
                {
                    break;
                }
                b.append(tmp, 0, len);
            }
            reader.close();
        }
        finally
        {
            reader.close();
        }
        return b.toString();
    }

    @Override
    protected void before() throws Throwable
    {
        super.before();
        stream = getClass().getResourceAsStream(res);
    }

    @Override
    protected void after()
    {
        try
        {
            stream.close();
        }
        catch (IOException e)
        {
            // ignore
        }
        if (file != null)
        {
            file.delete();
        }
        super.after();
    }

    private void createFile() throws IOException
    {
        file = new File(".",res);
        InputStream stream = getClass().getResourceAsStream(res);
        try
        {
            file.createNewFile();
            FileOutputStream ostream = null;
            try
            {
                ostream = new FileOutputStream(file);
                byte[] buffer = new byte[4096];
                while (true)
                {
                    int len = stream.read(buffer);
                    if (len < 0)
                    {
                        break;
                    }
                    ostream.write(buffer, 0, len);
                }
            }
            finally
            {
                if (ostream != null)
                {
                    ostream.close();
                }
            }
        }
        finally
        {
            stream.close();
        }
    }

}

Spring MVC offers a standaloneSetup that supports testing relatively simple controllers, without the need of context.

Build a MockMvc by registering one or more @Controller's instances and configuring Spring MVC infrastructure programmatically. This allows full control over the instantiation and initialization of controllers, and their dependencies, similar to plain unit tests while also making it possible to test one controller at a time.

An example test for your controller can be something as simple as

public class DemoApplicationTests {

    private MockMvc mockMvc;

    @Before
    public void setup() {
        this.mockMvc = MockMvcBuilders.standaloneSetup(new HelloWorld()).build();
    }

    @Test
    public void testSayHelloWorld() throws Exception {
        this.mockMvc.perform(get("/")
           .accept(MediaType.parseMediaType("application/json;charset=UTF-8")))
           .andExpect(status().isOk())
           .andExpect(content().contentType("application/json"));

    }
}

As of JUnit 4.11 you can use the ExpectedException rule's expectCause() method:

import static org.hamcrest.CoreMatchers.*;

// ...

@Rule
public ExpectedException expectedException = ExpectedException.none();

@Test
public void throwsNestedException() throws Exception {
    expectedException.expectCause(isA(SomeNestedException.class));

    throw new ParentException("foo", new SomeNestedException("bar"));
}