Monorepo migration breaks the pre-commit mvn test step

[burkedavison]

Although #1253 has been resolved, the mvn test step is now failing.

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.10.1:compile (default-compile) on project gapic-generator-java: Compilation failure: Compilation failure: 
[ERROR] /gapic-generator-java/gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/rest/ServiceClientTestClassComposer.java:[19,43] package com.google.api.gax.httpjson.testing does not exist
[ERROR] /gapic-generator-java/gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/rest/ServiceClientTestClassComposer.java:[24,38] package com.google.api.gax.rpc.testing does not exist
[ERROR] /gapic-generator-java/gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/grpc/ServiceClientTestClassComposer.java:[18,39] package com.google.api.gax.grpc.testing does not exist
[ERROR] /gapic-generator-java/gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/grpc/ServiceClientTestClassComposer.java:[19,39] package com.google.api.gax.grpc.testing does not exist
[ERROR] /gapic-generator-java/gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/grpc/ServiceClientTestClassComposer.java:[20,39] package com.google.api.gax.grpc.testing does not exist
[ERROR] /gapic-generator-java/gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/grpc/ServiceClientTestClassComposer.java:[21,39] package com.google.api.gax.grpc.testing does not exist

Attempting to fix this also unveils further issues with the next bazel integration test invocation.

[blakeli0]

Thanks Burke. I discussed this with a few folks as well, I personally don't rely on pre-commit but some folks are still using it, fixing pre-commit is on my TODO list. For now, you can always manually run unit tests and integration tests.

[lqiu96]

I think this is related to #1144 -- I think the temp workaround (which doesn't solve the mvn test issue at the root) is to cd into each module and run mvn test when needed.

[suztomo]

My attempt was using "verify" https://github.com/googleapis/gapic-generator-java/blob/main/.github/workflows/ci-maven.yaml#L75