Add "generatesSourcesExactly" method? about compile-testing HOT 3 OPEN

Compilation compilation = /* prepare your Compilation object */;

final ImmutableList<JavaFileObject> generatedSourceFiles = compilation.generatedSourceFiles();
final ImmutableList.Builder<String> builder = ImmutableList.builder();
for (JavaFileObject generatedSourceFile : generatedSourceFiles) {
    final String qualifiedName = generatedSourceFile.getName()
            .substring(StandardLocation.SOURCE_OUTPUT.getName().length() + 2)
            .replace(JavaFileObject.Kind.SOURCE.extension, "")
            .replace("/", ".");
    builder.add(qualifiedName);
}
final ImmutableList<String> generatedQualifiedNames = builder.build();

// Checking if expected files have been generated
Truth.assertThat(generatedQualifiedNames)
        .containsExactly("com.example.FileOne", "com.example.FileTwo", "com.example.FileThree");

// Checking if a specific file hasn't been generated
Truth.assertThat(generatedQualifiedNames)
        .doesNotContain("com.example.FileThatShouldntBeGenerated");

Truth.assertThat(generatedQualifiedNames)
        .comparingElementsUsing(SOURCE_FILE_CORRESPONDS_TO_QUALIFIED_NAME)
        .doesNotContain("com.example.FileThatShouldntBeGenerated");