bazel-java-test-suite-with_cfg-example

An example of using create_jvm_test_suite from https://github.com/bazel-contrib/rules_jvm along with https://github.com/fmeum/with_cfg.bzl to define a macro that creates Java test suites which can run tests on multiple versions of JDK, without having to define individual test targets for each test.

Demo

example/src/test/java has two Java source files containing JUnit tests:

❯ tree example/src/test/java/
example/src/test/java/
└── com
    └── mattnworb
        └── bazel
            ├── FailsOnJava17Test.java
            └── VersionTest.java

but Bazel sees variants of these two tests for running on jdk17 and jdk21:

❯ bazel query //example/... | grep -v _
...
//example:lib
//example:src/test/java/com/mattnworb/bazel/FailsOnJava17Test-jdk17
//example:src/test/java/com/mattnworb/bazel/FailsOnJava17Test-jdk21
//example:src/test/java/com/mattnworb/bazel/VersionTest-jdk17
//example:src/test/java/com/mattnworb/bazel/VersionTest-jdk21
//example:test-suite-jdk17
//example:test-suite-jdk21

in example/BUILD.bazel we define the tests with a java_test_suite macro which lives in tools/java/test_suite.bzl:

java_test_suite(
    name = "test-suite",
    test_runners = {
        "jdk21": java_21_junit5_test,
        "jdk17": java_17_junit5_test,
    },
    deps = JUNIT5_DEPS + [
        "lib",
        "@maven//:org_hamcrest_hamcrest",
        "@maven//:org_junit_jupiter_junit_jupiter_api",
    ],
)

this macro calls create_jvm_test_suite from contrib-rules-jvm once per entry in the test_runners attr, which allows for passing a custom java_test-like rule to define the test target to wrap the *Test.java file in via its define_test attr.

Normally create_jvm_test_suite would define the test with a name that is set based on the name and path of *Test.java file, but for this demo, we want to define multiple test variants for the same *Test.java file, so we apply a patch to create_jvm_test_suite in tools/java/contrib_rules_jvm_create_jvm_test_suite.patch which allows us to apply a suffix to the name attribute.

Running the demo

Note that the FailsOnJava17Test.java is intentionally set up to fail when run on version of the JDK, to demonstrate that the toolchain selection is working as we want:

❯ bazel test //example/... -t-
...
//example:src/test/java/com/mattnworb/bazel/FailsOnJava17Test-jdk21      PASSED in 0.5s
//example:src/test/java/com/mattnworb/bazel/VersionTest-jdk17            PASSED in 0.4s
//example:src/test/java/com/mattnworb/bazel/VersionTest-jdk21            PASSED in 0.5s
//example:src/test/java/com/mattnworb/bazel/FailsOnJava17Test-jdk17      FAILED in 0.5s

Running just the VersionTest, which prints out the java.specification.version and java.home properties shows different values for each JDK toolchain the test is run on:

❯ bazel test -t- --test_output=streamed \
  //example:src/test/java/com/mattnworb/bazel/VersionTest-jdk17 \
  //example:src/test/java/com/mattnworb/bazel/VersionTest-jdk21 \
...
java.specification.version: 21
java.vm.vendor: Amazon.com Inc.
java.home: /private/var/tmp/_bazel_mattbrown/54a55802995faae513241d7180d2e906/external/example_remotejdk_21_macos_aarch64
Failures: 0
java.specification.version: 17
java.vm.vendor: Amazon.com Inc.
java.home: /private/var/tmp/_bazel_mattbrown/54a55802995faae513241d7180d2e906/external/example_remotejdk_17_macos_aarch64
Failures: 0
INFO: Found 2 test targets...
INFO: Elapsed time: 0.779s, Critical Path: 0.32s
INFO: 3 processes: 1 internal, 2 darwin-sandbox.
INFO: Build completed successfully, 3 total actions
//example:src/test/java/com/mattnworb/bazel/VersionTest-jdk17            PASSED in 0.3s
//example:src/test/java/com/mattnworb/bazel/VersionTest-jdk21            PASSED in 0.3s

mattnworb/bazel-java-test-suite-with_cfg-example

bazel-java-test-suite-with_cfg-example

Demo

Running the demo