VSCode Java Tests

Extension to help write tests in Java using JUnit 4/5 with Hamcrest and Mockito.

Features:

• Snippets to add dependencies/plugins of test libs:
  • JUnit 5 and Vintage
  • JsonPath: Java DSL to facilitate the creation of JSON matchers
  • ArchUnit: Java DSL to test project architecture
  • JaCoCo: Code coverage report
  • Pitest: Mutation test
  • Testcontainers
• Snippets to write tests structures, assertions, mocks, so on
• Generate/open a test class for a given class
• Generate/open a class using its qualified name (like IntelliJ IDEA)

It generates the test class with configuration to run with JUnit 4 or 5 (depending on the option javaTests.template.junitDefaultVersion in VS Code).

I also recommend install Microsoft's Java Test Runner

How to Use

Commands

Command	Action	Description
java.tests.createTestClass	Create/Open Test File	Generate or open a test class
java.tests.createNewClass	Create new class	Generate or open a class from its qualified name

Snippets

Java

Prefix	Description
imports_junit4	Insert the imports for JUnit 4 (Mockito, Hamcrast and JUnit)
imports_junit5	Insert the imports for JUnit 5 (Mockito, Hamcrast and JUnit)
test_before	Create setup method with @Before
test_after	Create tear down method with @After
test_equals	assertEquals
test_is	assertThat with is
test_null	assertThat with nullValue
test_not_null	assertThat with notNullValue
test_nullorempty	assertThat with emptyOrNullString
test_not_nullorempty	assertThat with not(emptyOrNullString)
test_isOneOf	assertThat with isOneOf
test_hasSize	assertThat with hasSize
test_hasItem	assertThat with hasItem
test_hasItems	assertThat with hasItems
test_isIn	assertThat with isIn
mock_class	Create a mock object of a class
mock_method_return	Mock a method's return
mock_method_throw	Mock a method to throw exception
mock_verify_only	Verify if a mocked method was the only one called
mock_verify_once	Verify if a mocked method was called only once
mock_verify_times	Verify if a mocked method was called n times
mock_verify_never	Verify if a mocked method was never called
mock_arg_capture	Capture an argument given to a mocked method using ArgumentCaptor
test_exception	Assertion to verify if an exception was thrown (only JUnit 5)
test_parameterized	Create a parameterized test (only JUnit 5)

POM.xml

Snippets for Maven.

Prefix	Description
junit5-props	JUnit 5 verson properties
junit5-deps	JUnit 5 dependencies
junit5-vintage	JUnit 5 Vintage dependency to run tests from JUnit 3/4
surefire-dep	Surefire Maven dependency
failsafe-dep	Failsafe Maven dependency
archunit-junit5-dep	ArchUnit dependency to run with Junit 5
jsonpath-dep	JsonPath dependency to facilitate the creation of matchers for JSON
jacoco-plugin	Maven plugin for JaCoCo Code Coverage Library
pitest-plugin	Maven plugin for mutation test with Pitest
testcontainers-dep	Testcontainer dependencies
testcontainers-dep-management	Testcontainers Maven dependecy management

Actions

Create Test File

Generate a test class in the folder src/test/java with code to construct the source class, if already there is a test class then it will be opened.

Generate the test class with the following structure:

• All the types that are used by target Java class are imported (improvements pending)
• Define the instance to test using its first non-private constructor
• Define an attribute annotated with @Mock for each parameter from the first non-private constructor
• Define a test case for each public method that is not a setter (start with set and has only one parameter)
• Declare the variables to be passed as argument to the public method and to store the result, if needed

Example in JUnit 4

Given the file /src/main/java/com/github/sample/ObjectService.java:

package com.github.sample;

import java.util.logging.Logger;

import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;

@Service
public class ObjectService {
    private Logger logger;
    private ObjectRepository repository;

    private ObjectService(ObjectRepository repository) {
        this.repository = repository;
    }

    ObjectService(Logger logger, ObjectRepository repository) {
        this.logger = logger;
        this.repository = repository;
    }

    public void setLogger(Logger logger) {
        this.logger = logger;
    }

    public void save(Object object) {
        this.repository.save(object);
    }

    public Iterable<Object> fetchObjects() {
        return this.repository.findAll();
    }

    public Object findById(long id) {
        return this.repository.findById(id);
    }
}

@Repository

interface ObjectRepository extends CrudRepository<Object, Long> {
}

Generate the test file /src/test/java/com/github/sample/ObjectService.java:

package com.github.sample;

import static org.hamcrest.Matchers.*;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertThat;
import static org.mockito.Mockito.*;
import org.hamcrest.CoreMatchers;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.mockito.ArgumentCaptor;
import org.mockito.Mock;

// To be improved: only import the types that are used in the class API
import java.util.logging.Logger;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;

public class ObjectServiceTest {
    @Mock
    private Logger logger;
    @Mock
    private ObjectRepository repository;

    private ObjectService objectService;

    @Before
    public void setup() {
        this.objectService = new ObjectService(logger, repository);
    }

    @Test
    public void shouldSave() {
        // TODO: initialize args
        Object object;

        objectService.save(object);

        // TODO: assert scenario
    }

    @Test
    public void shouldFetchObjects() {
        Iterable<Object> actualValue = objectService.fetchObjects();

        // TODO: assert scenario
    }

    @Test
    public void shouldFindById() {
        // TODO: initialize args
        long id;

        Object actualValue = objectService.findById(id);

        // TODO: assert scenario
    }
}

Create New Class

Generate or open a class inside the folder src/main/java from a qualified class name (like IntelliJ IDEA).

Example

Give the input com.github.sample.ObjectService

Will generate a file /src/main/java/com/github/sample/ObjectService.java with the following content:

package com.github.sample;

public class ObjectService {

}

Known Bugs

• The generated test class tries to create a new instance even when there is only one private constructor

Roadmap

• Snippets to test
• Generate a test case for each method
• Create option to define if should mock the constructor's parameters
• Create option to define if should create a test case for each method
• Create option to ignore the static methods
• Generate template for JUnit 5 (imports, tests, checkers)
• Auto import the types used in arguments to constructor and methods
  • Improve to only import the types used in arguments to constructor and methods
• Snippets for Spring Boot tests (Rest Controller, Repository) - Doing
• Remember JUnit version by project
• Command to create the target class in src/main/java when doing TDD
• Create tests for the extension

Links

• Github Repository
• JUnit 5 Docs