Testing
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Vertx unit

Asynchronous polyglot unit testing.

Introduction

Vertx Unit is designed for writing asynchronous unit tests with a polyglot API and running these tests in the JVM. Vertx Unit Api borrows from existing test frameworks like JUnit or QUnit and follows the Vert.x practices.

As a consequence Vertx Unit is the natural choice for testing Vert.x applications.

To use vert.x unit, add the following dependency to the dependencies section of your build descriptor:

  • Maven (in your pom.xml):

<dependency>
 <groupId>io.vertx</groupId>
 <artifactId>vertx-unit</artifactId>
 <version>3.9.16</version>
 <scope>test</scope>
</dependency>

  • Gradle (in your build.gradle file):

testCompile ${io.vertx}:${vertx-unit}:3.9.16

Vert.x unit can be used in different ways and run anywhere your code runs, it is just a matter of reporting the results the right way, this example shows the bare minimum test suite:

TestSuite suite = TestSuite.create("the_test_suite");
suite.test("my_test_case", context -> {
  String s = "value";
  context.assertEquals("value", s);
});
suite.run();

The run method will execute the suite and go through all the tests of the suite. The suite can fail or pass, this does not matter if the outer world is not aware of the test result.

TestSuite suite = TestSuite.create("the_test_suite");
suite.test("my_test_case", context -> {
  String s = "value";
  context.assertEquals("value", s);
});
suite.run(new TestOptions().addReporter(new ReportOptions().setTo("console")));

When executed, the test suite now reports to the console the steps of the test suite:

Begin test suite the_test_suite
Begin test my_test
Passed my_test
End test suite the_test_suite , run: 1, Failures: 0, Errors: 0

The reporters option configures the reporters used by the suite runner for reporting the execution of the tests, see the Reporting section for more info.

Writing a test suite

A test suite is a named collection of test case, a test case is a straight callback to execute. The suite can have lifecycle callbacks to execute before and/or after the test cases or the test suite that are used for initializing or disposing services used by the test suite.

TestSuite suite = TestSuite.create("the_test_suite");
suite.test("my_test_case_1", context -> {
  // Test 1
});
suite.test("my_test_case_2", context -> {
  // Test 2
});
suite.test("my_test_case_3", context -> {
  // Test 3
});

The API is fluent and therefore the test cases can be chained:

TestSuite suite = TestSuite.create("the_test_suite");
suite.test("my_test_case_1", context -> {
  // Test 1
}).test("my_test_case_2", context -> {
  // Test 2
}).test("my_test_case_3", context -> {
  // Test 3
});

The test cases declaration order is not guaranteed, so test cases should not rely on the execution of another test case to run. Such practice is considered as a bad one.

Vertx Unit provides before and after callbacks for doing global setup or cleanup:

TestSuite suite = TestSuite.create("the_test_suite");
suite.before(context -> {
  // Test suite setup
}).test("my_test_case_1", context -> {
  // Test 1
}).test("my_test_case_2", context -> {
  // Test 2
}).test("my_test_case_3", context -> {
  // Test 3
}).after(context -> {
  // Test suite cleanup
});

The declaration order of the method does not matter, the example declares the before callback before the test cases and after callback after the test cases but it could be anywhere, as long as it is done before running the test suite.

The before callback is executed before any tests, when it fails, the test suite execution will stop and the failure is reported. The after callback is the last callback executed by the testsuite, unless the before callback reporter a failure.

Likewise, Vertx Unit provides the beforeEach and afterEach callback that do the same but are executed for each test case:

TestSuite suite = TestSuite.create("the_test_suite");
suite.beforeEach(context -> {
  // Test case setup
}).test("my_test_case_1", context -> {
  // Test 1
}).test("my_test_case_2", context -> {
  // Test 2
}).test("my_test_case_3", context -> {
  // Test 3
}).afterEach(context -> {
  // Test case cleanup
});

The beforeEach callback is executed before each test case, when it fails, the test case is not executed and the failure is reported. The afterEach callback is the executed just after the test case callback, unless the beforeEach callback reported a failure.

Asserting

Vertx Unit provides the TestContext object for doing assertions in test cases. The context object provides the usual methods when dealing with assertions.

assertEquals

Assert two objects are equals, works for basic types or json types.

suite.test("my_test_case", context -> {
  context.assertEquals(10, callbackCount);
});

There is also an overloaded version for providing a message:

suite.test("my_test_case", context -> {
  context.assertEquals(10, callbackCount, "Should have been 10 instead of " + callbackCount);
});

Usually each assertion provides an overloaded version.

assertNotEquals

The counter part of assertEquals.

suite.test("my_test_case", context -> {
  context.assertNotEquals(10, callbackCount);
});

assertNull

Assert an object is null, works for basic types or json types.

suite.test("my_test_case", context -> {
  context.assertNull(null);
});

assertNotNull

The counter part of assertNull.

suite.test("my_test_case", context -> {
  context.assertNotNull("not null!");
});

assertInRange

The assertInRange targets real numbers.

suite.test("my_test_case", context -> {

  // Assert that 0.1 is equals to 0.2 +/- 0.5

  context.assertInRange(0.1, 0.2, 0.5);
});

assertTrue and assertFalse

Asserts the value of a boolean expression.

suite.test("my_test_case", context -> {
  context.assertTrue(var);
  context.assertFalse(value > 10);
});

Failing

Last but not least, test provides a fail method that will throw an assertion error:

suite.test("my_test_case", context -> {
  context.fail("That should never happen");
  // Following statements won't be executed
});

The failure can either be a string as seen previously or an error. The error object depends on the target language, for Java or Groovy it can be any class extending Throwable- , for JavaScript it is an _error, for Ruby it is an Exception.

Using third-party assertion framework

It is also possible to use any other assertion framework, like the popular hamcrest and assertj. The recommended way to go is to use verify and perform the assertions within the supplied Handler. This way, asynchronous testing termination will be correctly handled.

suite.test("my_test_case", context -> context.verify(v -> {
  // Using here Assert from junit, could be assertj, hamcrest or any other
  // Even manually throwing an AssertionError.
  Assert.assertNotNull("not null!");
  Assert.assertEquals(10, callbackCount);
}));

Asynchronous testing

The previous examples supposed that test cases were terminated after their respective callbacks, this is the default behavior of a test case callback. Often it is desirable to terminate the test after the test case callback, for instance:

The Async object asynchronously completes the test case
suite.test("my_test_case", context -> {
  Async async = context.async();
  eventBus.consumer("the-address", msg -> {
    (2)
    async.complete();
  });
  (1)
});
1 The callback exits but the test case is not terminated
2 The event callback from the bus terminates the test

Creating an Async object with the async method marks the executed test case as non terminated. The test case terminates when the complete method is invoked.

When the complete callback is not invoked, the test case fails after a certain timeout.

Several Async objects can be created during the same test case, all of them must be completed to terminate the test.

Several Async objects provide coordination
suite.test("my_test_case", context -> {

  Async async1 = context.async();
  HttpClient client = vertx.createHttpClient();
  HttpClientRequest req = client.get(8080, "localhost", "/");
  req.exceptionHandler(err -> context.fail(err.getMessage()));
  req.handler(resp -> {
    context.assertEquals(200, resp.statusCode());
    async1.complete();
  });
  req.end();

  Async async2 = context.async();
  vertx.eventBus().consumer("the-address", msg -> {
    async2.complete();
  });
});

Async objects can also be used in before or after callbacks, it can be very convenient in a before callback to implement a setup that depends on one or several asynchronous results:

Async starts an http server before test cases
suite.before(context -> {
  Async async = context.async();
  HttpServer server = vertx.createHttpServer();
  server.requestHandler(requestHandler);
  server.listen(8080, ar -> {
    context.assertTrue(ar.succeeded());
    async.complete();
  });
});

It is possible to wait until the completion of a specific Async, similar to Java’s count-down latch:

Wait for completion
Async async = context.async();
HttpServer server = vertx.createHttpServer();
server.requestHandler(requestHandler);
server.listen(8080, ar -> {
  context.assertTrue(ar.succeeded());
  async.complete();
});

// Wait until completion
async.awaitSuccess();
this should not be executed from the event loop!

Async can also be created with an initial count value, it completes when the count-down reaches zero using countDown:

Wait until the complete count-down reaches zero
Async async = context.async(2);
HttpServer server = vertx.createHttpServer();
server.requestHandler(requestHandler);
server.listen(8080, ar -> {
  context.assertTrue(ar.succeeded());
  async.countDown();
});

vertx.setTimer(1000, id -> {
  async.complete();
});

// Wait until completion of the timer and the http request
async.awaitSuccess();

Calling complete() on an async completes the async as usual, it actually sets the value to 0.

Asynchronous assertions

TestContext provides useful methods that provides powerful constructs for async testing:

The asyncAssertSuccess method returns an {@literal Handler<AsyncResult<T>>} instance that acts like Async, resolving the Async on success and failing the test on failure with the failure cause.

Async async = context.async();
vertx.deployVerticle("my.verticle", ar -> {
  if (ar.succeeded()) {
    async.complete();
  } else {
    context.fail(ar.cause());
  }
});

// Can be replaced by

vertx.deployVerticle("my.verticle", context.asyncAssertSuccess());

The asyncAssertSuccess method returns an {@literal Handler<AsyncResult<T>>} instance that acts like Async, invoking the delegating {@literal Handler<T>} on success and failing the test on failure with the failure cause.

AtomicBoolean started = new AtomicBoolean();
Async async = context.async();
vertx.deployVerticle(new AbstractVerticle() {
  public void start() throws Exception {
    started.set(true);
  }
}, ar -> {
  if (ar.succeeded()) {
    context.assertTrue(started.get());
    async.complete();
  } else {
    context.fail(ar.cause());
  }
});

// Can be replaced by

vertx.deployVerticle("my.verticle", context.asyncAssertSuccess(id -> {
  context.assertTrue(started.get());
}));

The async is completed when the Handler exits, unless new asyncs were created during the invocation, which can be handy to chain asynchronous behaviors:

Async async = context.async();
vertx.deployVerticle("my.verticle", ar1 -> {
  if (ar1.succeeded()) {
    vertx.deployVerticle("my.otherverticle", ar2 -> {
      if (ar2.succeeded()) {
        async.complete();
      } else {
        context.fail(ar2.cause());
      }
    });
  } else {
    context.fail(ar1.cause());
  }
});

// Can be replaced by

vertx.deployVerticle("my.verticle", context.asyncAssertSuccess(id ->
        vertx.deployVerticle("my_otherverticle", context.asyncAssertSuccess())
));

The asyncAssertFailure method returns an {@literal Handler<AsyncResult<T>>} instance that acts like Async, resolving the Async on failure and failing the test on success.

Async async = context.async();
vertx.deployVerticle("my.verticle", ar -> {
  if (ar.succeeded()) {
    context.fail();
  } else {
    async.complete();
  }
});

// Can be replaced by

vertx.deployVerticle("my.verticle", context.asyncAssertFailure());

The asyncAssertFailure method returns an {@literal Handler<AsyncResult<T>>} instance that acts like Async, invoking the delegating {@literal Handler<Throwable>} on failure and failing the test on success.

Async async = context.async();
vertx.deployVerticle("my.verticle", ar -> {
  if (ar.succeeded()) {
    context.fail();
  } else {
    context.assertTrue(ar.cause() instanceof IllegalArgumentException);
    async.complete();
  }
});

// Can be replaced by

vertx.deployVerticle("my.verticle", context.asyncAssertFailure(cause -> {
  context.assertTrue(cause instanceof IllegalArgumentException);
}));

The async is completed when the Handler exits, unless new asyncs were created during the invocation.

Repeating test

When a test fails randomly or not often, for instance a race condition, it is convenient to run the same test multiple times to increase the failure likelihood of the test.

Repeating a test
TestSuite.create("my_suite").test("my_test", 1000, context -> {
  // This will be executed 1000 times
});

When declared, beforeEach and afterEach callbacks will be executed as many times as the test is executed.

test repetition are executed sequentially

Sharing objects

The TestContext has get/put/remove operations for sharing state between callbacks.

Any object added during the before callback is available in any other callbacks. Each test case will operate on a copy of the shared state, so updates will only be visible for a test case.

Sharing state between callbacks
TestSuite.create("my_suite").before(context -> {

  // host is available for all test cases
  context.put("host", "localhost");

}).beforeEach(context -> {

  // Generate a random port for each test
  int port = helper.randomPort();

  // Get host
  String host = context.get("host");

  // Setup server
  Async async = context.async();
  HttpServer server = vertx.createHttpServer();
  server.requestHandler(req -> {
    req.response().setStatusCode(200).end();
  });
  server.listen(port, host, ar -> {
    context.assertTrue(ar.succeeded());
    context.put("port", port);
    async.complete();
  });

}).test("my_test", context -> {

  // Get the shared state
  int port = context.get("port");
  String host = context.get("host");

  // Do request
  HttpClient client = vertx.createHttpClient();
  HttpClientRequest req = client.get(port, host, "/resource");
  Async async = context.async();
  req.handler(resp -> {
    context.assertEquals(200, resp.statusCode());
    async.complete();
  });
  req.end();
});
sharing any object is only supported in Java, other languages can share only basic or json types. Other objects should be shared using the features of that language.

Running

When a test suite is created, it won’t be executed until the run method is called.

Running a test suite
suite.run();

The test suite can also be run with a specified Vertx instance:

Provides a Vertx instance to run the test suite
suite.run(vertx);

When running with a Vertx instance, the test suite is executed using the Vertx event loop, see the Event loop section for more details.

A test suite can be run with the Vert.x Command Line Interface with the vertx test command:

Running a test suite with the Vert.x CLI
> vertx test the_test_suite.js
Begin test suite the_test_suite
Succeeded in deploying verticle
Begin test my_test_case
Passed my_test_case
End test suite my_suite , run: 1, Failures: 0, Errors: 0

Such test suite just need to be executed via the run command, the vertx test command takes care of configuring reporting, timeout, etc…​, pretty much like in this example:

TestSuite suite = TestSuite.create("the_test_suite");
suite.test("my_test_case", context -> {
  String s = "value";
  context.assertEquals("value", s);
});
suite.run();

The vertx test command extends the vertx run command. The exit behavior of the JVM is changed the JVM exits when the test suite is executed and a return value is provided indicating the tests success (0) or failure (1).

several test suites can executed in the same verticle, Vert.x Unit waits until completion of all suite executed.

Test suite completion

No assumptions can be made about when the test suite will be completed, and if some code needs to be executed after the test suite, it should either be in the test suite after callback or as callback of the Completion:

Test suite execution callback
TestCompletion completion = suite.run(vertx);

// Simple completion callback
completion.handler(ar -> {
  if (ar.succeeded()) {
    System.out.println("Test suite passed!");
  } else {
    System.out.println("Test suite failed:");
    ar.cause().printStackTrace();
  }
});

The Completion object provides also a resolve method that takes a Promise object, this Promise will be notified of the test suite execution:

Resolving the start Promise with the test suite
TestCompletion completion = suite.run();

// When the suite completes, the promise is resolved
completion.resolve(startPromise);

This allow to easily create a test verticle whose deployment is the test suite execution, allowing the code that deploys it to be easily aware of the success or failure.

The completion object can also be used like a latch to block until the test suite completes. This should be used when the thread running the test suite is not the same than the current thread:

Blocking until the test suite completes
Completion completion = suite.run();

// Wait until the test suite completes
completion.await();

The await throws an exception when the thread is interrupted or a timeout is fired.

The awaitSuccess is a variation that throws an exception when the test suite fails.

Blocking until the test suite succeeds
Completion completion = suite.run();

// Wait until the test suite succeeds otherwise throw an exception
completion.awaitSuccess();

Time out

Each test case of a test suite must execute before a certain timeout is reached. The default timeout is of 2 minutes, it can be changed using test options:

Setting the test suite timeout
TestOptions options = new TestOptions().setTimeout(10000);

// Run with a 10 seconds time out
suite.run(options);

Event loop

Vertx Unit execution is a list of tasks to execute, the execution of each task is driven by the completion of the previous task. These tasks should leverage Vert.x event loop when possible but that depends on the current execution context (i.e the test suite is executed in a main or embedded in a Verticle) and wether or not a Vertx instance is configured.

The setUseEventLoop configures the usage of the event loop:

Table 1. Event loop usage
useEventLoop:null useEventLoop:true useEventLoop:false

Vertx instance

use vertx event loop

use vertx event loop

force no event loop

in a Verticle

use current event loop

use current event loop

force no event loop

in a main

use no event loop

raise an error

use no event loop

The default useEventLoop value is null, that means that it will uses an event loop when possible and fallback to no event loop when no one is available.

Reporting

Reporting is an important piece of a test suite, Vertx Unit can be configured to run with different kind of reporters.

By default no reporter is configured, when running a test suite, test options can be provided to configure one or several:

Using the console reporter and as a junit xml file
ReportOptions consoleReport = new ReportOptions().
    setTo("console");

// Report junit files to the current directory
ReportOptions junitReport = new ReportOptions().
    setTo("file:.").
    setFormat("junit");

suite.run(new TestOptions().
        addReporter(consoleReport).
        addReporter(junitReport)
);

Console reporting

Reports to the JVM System.out and System.err:

to

console

format

simple or junit

File reporting

Reports to a file, a Vertx instance must be provided:

to

file : dir name

format

simple or junit

example

file:.

The file reporter will create files in the configured directory, the files will be named after the test suite name executed and the format (i.e simple creates txt files and junit creates xml files).

Log reporting

Reports to a logger, a Vertx instance must be provided:

to

log : logger name

example

log:mylogger

Event bus reporting

Reports events to the event bus, a Vertx instance must be provided:

to

bus : event bus address

example

bus:the-address

It allow to decouple the execution of the test suite from the reporting.

The messages sent over the event bus can be collected by the EventBusCollector and achieve custom reporting:

EventBusCollector collector = EventBusCollector.create(
    vertx,
    new ReportingOptions().addReporter(
        new ReportOptions().setTo("file:report.xml").setFormat("junit")));

collector.register("the-address");

Vertx integration

By default, assertions and failures must be done on the TestContext and throwing an assertion error works only when called by Vert.x Unit:

suite.test("my_test_case", ctx -> {

  // The failure will be reported by Vert.x Unit
  throw new RuntimeException("it failed!");
});

In a regular Vert.x callback, the failure will be ignored:

suite.test("test-server", testContext -> {
  HttpServer server = vertx.createHttpServer().requestHandler(req -> {
    if (req.path().equals("/somepath")) {
      throw new AssertionError("Wrong path!");
    }
    req.response().end();
  });
});

Since Vert.x 3.3, a global exception handler can be set to report the event loop uncaught exceptions:

suite.before(testContext -> {

  // Report uncaught exceptions as Vert.x Unit failures
  vertx.exceptionHandler(testContext.exceptionHandler());
});

suite.test("test-server", testContext -> {
  HttpServer server = vertx.createHttpServer().requestHandler(req -> {
    if (req.path().equals("/somepath")) {
      throw new AssertionError("Wrong path!");
    }
    req.response().end();
  });
});

The exception handler is set during the before phase, the TestContext is shared between each before, test and after phase. So the exception handler obtained during the before phase is correct.

Junit integration

Although Vertx Unit is polyglot and not based on JUnit, it is possible to run a Vertx Unit test suite or a test case from JUnit, allowing you to integrate your tests with JUnit and your build system or IDE.

Run a Java class as a JUnit test suite
@RunWith(VertxUnitRunner.class)
public class JUnitTestSuite {
  @Test
  public void testSomething(TestContext context) {
    context.assertFalse(false);
  }
}

The VertxUnitRunner uses the junit annotations for introspecting the class and create a test suite after the class. The methods should declare a TestContext argument, if they don’t it is fine too. However the TestContext is the only way to retrieve the associated Vertx instance of perform asynchronous tests.

The JUnit integration is also available for the Groovy language with the io.vertx.groovy.ext.unit.junit.VertxUnitRunner runner.

Running a test on a Vert.x context

By default the thread invoking the test methods is the JUnit thread. The RunTestOnContext JUnit rule can be used to alter this behavior for running these test methods with a Vert.x event loop thread.

Thus there must be some care when state is shared between test methods and Vert.x handlers as they won’t be on the same thread, e.g incrementing a counter in a Vert.x handler and asserting the counter in the test method. One way to solve this is to use proper synchronization, another is to execute test methods on a Vert.x context that will be propagated to the created handlers.

For this purpose the RunTestOnContext rule needs a Vertx instance. Such instance can be provided, otherwise the rule will manage an instance under the hood. Such instance can be retrieved when the test is running, making this rule a way to manage a Vertx instance as well.

Run a Java class as a JUnit test suite
@RunWith(VertxUnitRunner.class)
public class RunOnContextJUnitTestSuite {

  @Rule
  public RunTestOnContext rule = new RunTestOnContext();

  @Test
  public void testSomething(TestContext context) {
    // Use the underlying vertx instance
    Vertx vertx = rule.vertx();
  }
}

The rule can be annotated by {@literal @Rule} or {@literal @ClassRule}, the former manages a Vert.x instance per test, the later a single Vert.x for the test methods of the class.

keep in mind that you cannot block the event loop when using this rule. Usage of classes like CountDownLatch or similar classes must be done with care.

Timeout

The Vert.x Unit 2 minutes timeout can be overriden with the timeout member of the @Test annotation:

Configure the timeout at the test level
public class JunitTestWithTimeout {

  @Test(timeout = 1000l)
  public void testSomething(TestContext context) {
    //...
  }

}

For a more global configuration, the Timeout rule can be used:

Configure the timeout at the class level
@RunWith(VertxUnitRunner.class)
public class TimeoutTestSuite {

  @Rule
  public Timeout rule = Timeout.seconds(1);

  @Test
  public void testSomething(TestContext context) {
    //...
  }
}
the @Test timeout overrides the the Timeout rule.

Parameterized tests

JUnit provides useful Parameterized tests, Vert.x Unit tests can be ran with this particular runner thanks to the VertxUnitRunnerWithParametersFactory:

Running a Vert.x Unit parameterized test
@RunWith(Parameterized.class)
@Parameterized.UseParametersRunnerFactory(VertxUnitRunnerWithParametersFactory.class)
public class SimpleParameterizedTest {

  @Parameterized.Parameters
  public static Iterable<Integer> data() {
    return Arrays.asList(0, 1, 2);
  }

  public SimpleParameterizedTest(int value) {
    //...
  }

  @Test
  public void testSomething(TestContext context) {
    // Execute test with the current value
  }
}

Parameterized tests can also be done in Groovy with the io.vertx.groovy.ext.unit.junit.VertxUnitRunnerWithParametersFactory.

Repeating a test

When a test fails randomly or not often, for instance a race condition, it is convenient to run the same test multiple times to increase the likelihood failure of the test.

With JUnit a test has to be annotated with @Repeat to be repeated. The test must also define the RepeatRule among its rules.

Repeating a test with JUnit
@RunWith(VertxUnitRunner.class)
public class RepeatingTest {

  @Rule
  public RepeatRule rule = new RepeatRule();

  @Repeat(1000)
  @Test
  public void testSomething(TestContext context) {
    // This will be executed 1000 times
  }
}

When declared, before and after life cycle will be executed as many times as the test is executed.

test repetition are executed sequentially

Using with other assertion libraries

Vert.x Unit usability has been greatly improved in Vert.x 3.3. You can now write tests using Hamcrest, AssertJ, Rest Assured, or any assertion library you want. This is made possible by the global exception handler described in Vertx integration.

You can find Java examples of using Vert.x Unit with Hamcrest and AssertJ in the vertx-examples project.

Java language integration

Test suite integration

The Java language provides classes and it is possible to create test suites directly from Java classes with the following mapping rules:

The testSuiteObject argument methods are inspected and the public, non static methods with TestContext parameter are retained and mapped to a Vertx Unit test suite via the method name:

  • before : before callback

  • after : after callback

  • beforeEach : beforeEach callback

  • afterEach : afterEach callback

  • when the name starts with test : test case callback named after the method name

Test suite written using a Java class
public class MyTestSuite {

  public void testSomething(TestContext context) {
    context.assertFalse(false);
  }
}

This class can be turned into a Vertx test suite easily:

Create a test suite from a Java object
TestSuite suite = TestSuite.create(new MyTestSuite());