test: introduce basic unit tests

ruby/tests/BUILD

@@ -0,0 +1,3 @@
+load(":utils_tests.bzl", "utils_test_suite")
+
+utils_test_suite()

ruby/tests/utils_tests.bzl

@@ -0,0 +1,18 @@
+"""Unit tests for utils."""
+
+load("@bazel_skylib//lib:unittest.bzl", "asserts", "unittest")
+load(
+    "//ruby/private:utils.bzl",
+    _normalize_bzlmod_repository_name = "normalize_bzlmod_repository_name",
+)
+
+def _normalize_bzlmod_repository_name_test_impl(ctx):
+    env = unittest.begin(ctx)
+    asserts.equals(env, _normalize_bzlmod_repository_name("bundle"), "bundle")
+    asserts.equals(env, _normalize_bzlmod_repository_name("rules_ruby~override~ruby~bundle"), "bundle")
+    return unittest.end(env)
+
+normalize_bzlmod_repository_name_test = unittest.make(_normalize_bzlmod_repository_name_test_impl)
+
+def utils_test_suite():
+    unittest.suite("utils_tests", normalize_bzlmod_repository_name_test)