Resolving Vert.x Context Issues in Quarkus Reactive Panache with Mockito

Understanding the Vert.x Context Error in Quarkus Reactive Panache Testing

When building a Quarkus application using Hibernate Reactive with Panache, ensuring non-blocking database operations is crucial. However, as developers move towards writing tests for these operations, they might encounter specific challenges. One such issue arises when working with Panache's reactive model in Quarkus testing.

A common error that developers face is the "No current Vertx context found" message. This error typically appears when testing a service method wrapped inside a reactive transaction using Panache.withTransaction(). It's related to the underlying Vert.x framework, which requires the right context for these non-blocking operations.

The challenge lies in configuring the test environment properly to run within the correct Vert.x context. Mocking and stubbing database interactions, while helpful, often does not resolve this problem fully. As a result, the test might fail even when the service code works perfectly in production.

In this article, we will explore how to handle this issue in Quarkus and how to configure your test cases for successful execution. We'll dive into the reasons behind the error and provide a step-by-step guide on setting up the correct Vert.x context.

Handling Vert.x Context and Reactive Panache Testing in Quarkus

In the first solution, the key challenge is the missing Vert.x context when performing tests on reactive database operations. Quarkus provides the @TestReactiveTransaction annotation, which ensures that the test runs within a reactive transaction, setting up the necessary Vert.x context. This is crucial for making sure that Panache's non-blocking database operations, like Panache.withTransaction(), can run properly without throwing the “No current Vert.x context found” error. By adding this annotation, we automatically configure the right environment, allowing the test to mimic real transactional behavior.

In the second solution, we manually create the Vert.x context using VertxContextSupport.runOnContext(). This approach ensures that the reactive code, particularly the database operations managed by Panache, runs inside the Vert.x event loop. By doing so, we provide a valid Vert.x context during the test. This is especially useful when more control over the test environment is required. Additionally, mocking Panache’s operations with PanacheMock.mock() ensures that the database-related code can be isolated for testing without hitting an actual database.

The third solution leverages the Uni.createFrom().context() method to manually create and manage the Vert.x context within the reactive stream. This method allows the developer to define a custom context for asynchronous Panache operations during testing, ensuring that all reactive actions are performed in a proper environment. This method is particularly useful when testing asynchronous or non-blocking code, as it ensures smooth handling of both the context and the reactive data flows.

Throughout these solutions, Mockito.when() plays an important role in mocking the behavior of the Panache methods. By using this method, we control the outcome of operations like Panache.withTransaction() and User.persist(), allowing us to simulate different scenarios (e.g., success or failure of database operations). Combining these solutions allows developers to fully test the Panache reactive flows in Quarkus without dealing with issues related to asynchronous handling or the lack of a proper Vert.x context.

// Solution 1: Use TestReactiveTransaction to ensure a proper Vert.x context in your test.
@TestReactiveTransaction
@QuarkusTest
public class AuthServiceTest {
    @Inject
    AuthService authService;

    @Test
    void testCreateUserWithVertxContext() {
        Uni<Auth> result = authService.createUser(new Auth("test@gmail.com", "test123"));
        result.subscribe().with(auth -> {
            assertEquals("test@gmail.com", auth.getEmail());
        });
    }
}

// Solution 2: Mock the Vert.x context manually for your Panache operations.
@QuarkusTest
public class AuthServiceTest {
    @Inject
    AuthService authService;

    @BeforeEach
    void setup() {
        Vertx vertx = Vertx.vertx();
        VertxContextSupport.runOnContext(vertx, () -> {
            // Setup for Panache mock
            PanacheMock.mock(User.class);
            PanacheMock.mock(Panache.class);
        });
    }

    @Test
    void testCreateUserInMockedContext() {
        Mockito.when(Panache.withTransaction(any())).thenReturn(Uni.createFrom().item(new Auth("mock@gmail.com", "password123")));
        Auth auth = authService.createUser(new Auth("mock@gmail.com", "password123")).await().indefinitely();
        assertEquals("mock@gmail.com", auth.getEmail());
    }
}

// Solution 3: Use Uni.createFrom().context to create and manage a Vert.x context for reactive testing.
@QuarkusTest
public class AuthServiceTest {
    @Inject
    AuthService authService;

    @Test
    void testVertxContextSetupForReactivePanache() {
        Uni.createFrom().context(context -> {
            return authService.createUser(new Auth("reactive@gmail.com", "password123"));
        }).subscribe().with(auth -> {
            assertEquals("reactive@gmail.com", auth.getEmail());
        });
    }
}

Addressing the Importance of Vert.x Context in Quarkus Testing

When working with reactive systems like Quarkus, especially with frameworks such as Hibernate Reactive and Panache, managing the Vert.x context becomes a crucial aspect. The Vert.x context is necessary for executing non-blocking code in a structured and controlled manner. Without it, as seen in the common "No current Vertx context found" error, reactive operations like Panache.withTransaction() will fail during tests. This occurs because Quarkus uses Vert.x under the hood to manage asynchronous, non-blocking I/O, and every reactive database operation needs to be wrapped in the appropriate context.

Developers often face difficulties in testing these reactive methods due to the absence of a valid Vert.x context during the test lifecycle. The typical testing environment does not automatically provide this context unless explicitly set up, causing issues when mocking database operations. However, the use of tools like TestReactiveTransaction or manually creating the Vert.x context within the test environment can solve these challenges. This method ensures that the tests closely mimic the behavior of the application in production, where a Vert.x context is always present.

Furthermore, reactive testing requires extra attention to synchronization. Reactive streams, like the Uni from SmallRye Mutiny, handle asynchronous data flows, meaning that without proper context handling, operations can be executed on different threads, leading to failures. The solution often lies in not only mocking the methods but also ensuring that the test runs within the correct reactive transactional boundaries. This way, developers can avoid errors and successfully simulate real-world use cases in a controlled test environment.