Test Suite with JUnit

MicroEJ allows to run unit tests using the standard JUnit API during the build process of a MicroEJ library or a MicroEJ Application. The MicroEJ Test Suite Engine runs tests on a target Platform and outputs a JUnit XML report.


JUnit testing can be enabled when using the microej-javalib (MicroEJ Add-On Library) or the microej-application (MicroEJ Applications) build type. JUnit test cases processing is automatically enabled when the following dependency is declared in the module.ivy file of the project.

<dependency conf="test->*" org="ej.library.test" name="junit" rev="1.5.0"/>

When a new JUnit test case class is created in the src/test/java folder, a JUnit processor generates MicroEJ compliant classes into a specific source folder named src-adpgenerated/junit/java. These files are automatically managed and must not be edited manually.

JUnit Compliance

MicroEJ is compliant with a subset of JUnit version 4. MicroEJ JUnit processor supports the following annotations: @After, @AfterClass, @Before, @BeforeClass, @Ignore, @Test.

Each test case entry point must be declared using the org.junit.Test annotation (@Test before a method declaration). Please refer to JUnit documentation to get details on usage of other annotations.

Setup a Platform for Tests

Before running tests, a target platform must be configured.

Execution in SDK

In order to execute the Test Suite in the SDK, a target platform must be configured in the MicroEJ workspace. The following steps assume that a platform has been previously imported into the MicroEJ Platform repository (or available in the Workspace):

  • Go to Window > Preferences > MicroEJ > Platforms (or Platforms in workspace).
  • Select the desired platform on which to run the tests.
  • Press F2 to expand the details.
  • Select the the platform path and copy it to the clipboard.
  • Go to Window > Preferences > Ant > Runtime and select the Properties tab.
  • Click on Add Property… button and set a new property named target.platform.dir with the platform path pasted from the clipboard.

Execution during module build

In order to execute the Test Suite during the build of the module, a target platform must be configured in the module project as described in the section Platform Selection.

Setup a Project with a JUnit Test Case

This section describes how to create a new JUnit Test Case starting from a new MicroEJ library project.

  • First create a new module project using the microej-javalib skeleton. A new project named mylibrary is created in the workspace.
  • Right-click on the src/test/java folder and select New > Other… menu item.
  • Select the Java > JUnit > New JUnit Test Case wizard.
  • Enter a test name and press Finish. A new JUnit test case class is created with a default failing test case.

Build and Run a JUnit Test Suite

  • Right-click on the mylibrary project and select Build Module. After the library is built, the test suite engine launches available test cases and the build process fails in the console view.
  • On the mylibrary project, right-click and select Refresh. A target~ folder appears with intermediate build files. The JUnit report is available at target~\test\xml\TEST-test-report.xml.
  • Double-click on the file to open the JUnit test suite report.
  • Modify the test case by replacing
fail("Not yet implemented");


  • Right-click again on the mylibrary project and select Build Module. The test is now successfully executed on the target platform so the MicroEJ Add-On Library is fully built and published without errors.
  • Double-click on the JUnit test suite report to see the test has been successfully executed.

Test Suite Reports

Once a test suite is completed, the following test suite reports are generated:

  • JUnit HTML report in the module project location target~/test/html/test/junit-noframes.html. This report contains a summary and the execution trace of every executed test.

    Example of MicroEJ Test Suite HTML Report

    Example of MicroEJ Test Suite HTML Report

  • JUnit XML report in the module project location target~/test/xml/TEST-test-report.xml.

    Example of MicroEJ Test Suite XML Report

    Example of MicroEJ Test Suite XML Report

    XML report file can also be open in the JUnit View. Right-click on the file > Open With > JUnit View:

    Example of MicroEJ Test Suite XML Report in JUnit View

    Example of MicroEJ Test Suite XML Report in JUnit View

If executed on device, the Firmware binary produced for each test is available in module project location target~/test/xml/<TIMESTAMP>/bin/<FULLY-QUALIFIED-CLASSNAME>/application.out.

Advanced Configurations

Autogenerated Test Classes

The JUnit processor generates test classes into the src-adpgenerated/junit/java folder. This folder contains:

_AllTestClasses.java file
A single class with a main enty point that sequentially calls all declared test methods of all JUnit test case classes.
_AllTests_[TestCase].java files
For each JUnit test case class, a class with a main entry point that sequentially calls all declared test methods.
_SingleTest_[TestCase]_[TestMethod].java files
For each test method of each JUnit test case class, a class with a main entry point that calls the test method.

JUnit Test Case to MicroEJ Test Case

The MicroEJ Test Suite Engine allows to select the classes that will be executed, by setting the following property in the project module.ivy file.

<ea:property name="test.run.includes.pattern" value="[MicroEJ Test Case Include Pattern]"/>

The following line consider all JUnit test methods of the same class as a single MicroEJ test case (default behaviour). If at least one JUnit test method fails, the whole test case fails in the JUnit report.

<ea:property name="test.run.includes.pattern" value="**/_AllTests_*.class"/>

The following line consider each JUnit test method as a dedicated MicroEJ test case. Each test method is viewed independently in the JUnit report, but this may slow down the test suite execution because a new deployment is done for each test method.

<ea:property name="test.run.includes.pattern" value="**/_SingleTest_*.class"/>

Run a Single Test Manually

Each test can be run independently as each class contains a main entry point.

In the src-adpgenerated/junit/java folder, right-click on the desired autogenerated class (_SingleTest_[TestCase]_[TestMethod].java) and select Run As > MicroEJ Application.

The test is executed on the selected Platform and the output result is dumped into the console.

Test Suite Options

The MicroEJ Test Suite Engine can be configured with specific options which can be added to the module.ivy file of the project running the test suite, within the <ea:build> XML element.

  • Application Option Injection

    It is possible to inject an Application Option for all the tests, by adding to the original option the microej.testsuite.properties. prefix:

    <ea:property name="microej.testsuite.properties.[application_option_name]" value="[application_option_value]"/>
  • Retry Mechanism

    A test execution may not be able to produce the success trace for an external reason, for example an unreliable harness script that may lose some trace characters or crop the end of the trace. For all these unlikely reasons, it is possible to configure the number of retries before a test is considered to have failed:

    <ea:property name="microej.testsuite.retry.count" value="[nb_of_retries]"/>

    By default, when a test has failed, it is not executed again (option value is set to 0).

Test Specific Options

The MicroEJ Test Suite Engine allows to define Application Options specific to each test case. This can be done by defining a file with the same name as the generated test case file with the .properties extension instead of the .java extension. The file must be put in the src/test/resources folder and within the same package than the test case file.