Add rules to the test_deps target. (#102)

* Add rules to the test_deps target.

Likely needed for anyone doing integration tests using skylib.

* Default public visibility and only tag things that are private.

BUILD

@@ -15,6 +15,7 @@ filegroup(
     srcs = [
         "BUILD",
         "//lib:test_deps",
+        "//rules:test_deps",
         "//toolchains/unittest:test_deps",
     ] + glob(["*.bzl"]),
 )

rules/BUILD

@@ -2,16 +2,16 @@ load("//:bzl_library.bzl", "bzl_library")
 
 licenses(["notice"])
 
+package(default_visibility = ["//visibility:public"])
+
 bzl_library(
     name = "build_test",
     srcs = ["build_test.bzl"],
-    visibility = ["//visibility:public"],
 )
 
 bzl_library(
     name = "maprule",
     srcs = ["maprule.bzl"],
-    visibility = ["//visibility:public"],
     deps = [":maprule_private"],
 )
 
@@ -28,3 +28,12 @@ bzl_library(
 # Exported for build_test.bzl to make sure of, it is an implementation detail
 # of the rule and should not be directly used by anything else.
 exports_files(["empty_test.sh"])
+
+filegroup(
+    name = "test_deps",
+    testonly = True,
+    srcs = [
+        "BUILD",
+        "empty_test.sh",
+    ] + glob(["*.bzl"]),
+)