The

assert_build_context

requests this product from the rule runner:

context = rule_runner.request(
        DockerBuildContext,
        [
            DockerBuildContextRequest(
                address=address,
                build_upstream_images=False,
            )
        ],
    )

And the rule runner has these rules:

return RuleRunner(
        rules=[
            *context_rules(),
            *core_target_types_rules(),
            *package_pex_binary.rules(),
            *pex_from_targets.rules(),
            *target_types_rules.rules(),
            QueryRule(BuiltPackage, [PexBinaryFieldSet]),
            QueryRule(DockerBuildContext, (DockerBuildContextRequest,)),
        ],
        target_types=[DockerImage, Files, PexBinary],
    )

where most of those rules are taken from the

package_pex_binary_integration_test

.