Why can't Bazel find my test class when running bazel test on a java_test rule?

Question

I have a test class defined in src/handlers/MyHttpHandlerTest.java (sorry, I know it's best practice to put tests in a tests directory).

Here is my src/handlers/BUILD file:

java_test(
    name = "MyHttpHandlerTest",
    srcs = [
        "MyHttpHandler.java",
        "MyHttpHandlerTest.java",
    ],
    deps = [
        "//:java_test_deps",
        "//src/messages",
    ],
)

My test class is defined in src/handlers/MyHttpHandlerTest.java as follows (It currently doesn't assert anything -- I'm just trying to test out my installation of junit and Mockito):

package src.handlers;

import com.sun.net.httpserver.HttpExchange;
import src.messages.Message;

import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.mockito.Mockito.when;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;

import java.io.IOException;

@ExtendWith(MockitoExtension.class)
public class MyHttpHandlerTest {

    @Mock
    Message message;

    @Mock
    HttpExchange exchange;

    @Test
    public void testGetMessage() throws IOException {
        MyHttpHandler handler = new MyHttpHandler();
        when(message.getMessage()).thenReturn("Hello world!");
        handler.setMessage(message);
        handler.handle(exchange);
    }
}

When I run bazel test //src/handlers:MyHttpHandlerTest, it successfully compiles the source files, but then returns the error:

Class not found: [handlers.MyHttpHandlerTest]

Why can't bazel find this class?

Answer 1

Bazel guesses that the the root of the Java package hierarchy is the src folder and therefore tries to load handlers.MyHttpHandlerTest. So, either change the package to actually be handlers or override Bazel's heuristic with the test_class attribute:

java_test(
    name = "MyHttpHandlerTest",
    srcs = [
        "MyHttpHandler.java",
        "MyHttpHandlerTest.java",
    ],
    deps = [
        "//:java_test_deps",
        "//src/messages",
    ],
    test_class = "src.handlers.MyHttpHandlerTest",
)