diff --git a/README.md b/README.md
index e06c0f5..2c9251c 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,8 @@ be loaded as a single unit, for convenience.
 
 ## Getting Started
 
+### `WORKSPACE` file
+
 Add the following to your `WORKSPACE` file to import the Skylib repository into
 your workspace. Replace the version number in the `tag` attribute with the
 version you wish to depend on:
@@ -28,6 +30,17 @@ git_repository(
 )
 ```
 
+If you want to use `lib/unittest.bzl` from Skylib versions released in or after
+December 2018, then you also should add to the `WORKSPACE` file:
+
+```python
+load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
+
+bazel_skylib_workspace()
+```
+
+### `BUILD` and `*.bzl` files
+
 Then, in the `BUILD` and/or `*.bzl` files in your own workspace, you can load
 the modules (listed [below](#list-of-modules)) and access the symbols by
 dotting into those structs:
@@ -85,3 +98,15 @@ Steps to add a module to Skylib:
 The `bzl_library.bzl` rule can be used to aggregate a set of
 Starlark files and its dependencies for use in test targets and
 documentation generation.
+
+## Troubleshooting
+
+If you try to use `unittest` and you get the following error:
+
+```
+ERROR: While resolving toolchains for target //foo:bar: no matching toolchains found for types @bazel_skylib//toolchains:toolchain_type
+ERROR: Analysis of target '//foo:bar' failed; build aborted: no matching toolchains found for types @bazel_skylib//toolchains:toolchain_type
+```
+
+then you probably forgot to load and call `bazel_skylib_workspace()` in your
+`WORKSPACE` file.
diff --git a/WORKSPACE b/WORKSPACE
index 5458cd5..e0f2a0a 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -1 +1,5 @@
 workspace(name = "bazel_skylib")
+
+load(":workspace.bzl", "bazel_skylib_workspace")
+
+bazel_skylib_workspace()
diff --git a/lib/unittest.bzl b/lib/unittest.bzl
index 7489890..8ceb51f 100644
--- a/lib/unittest.bzl
+++ b/lib/unittest.bzl
@@ -22,6 +22,43 @@ assertions used to within tests.
 load(":new_sets.bzl", new_sets = "sets")
 load(":sets.bzl", "sets")
 
+# The following function should only be called from WORKSPACE files and workspace macros.
+def register_unittest_toolchains():
+    """Registers the toolchains for unittest users."""
+    native.register_toolchains(
+        "@bazel_skylib//toolchains/unittest:cmd_toolchain",
+        "@bazel_skylib//toolchains/unittest:bash_toolchain",
+    )
+
+TOOLCHAIN_TYPE = "@bazel_skylib//toolchains/unittest:toolchain_type"
+
+_UnittestToolchain = provider(
+    doc = "Execution platform information for rules in the bazel_skylib repository.",
+    fields = ["file_ext", "success_templ", "failure_templ", "join_on"],
+)
+
+def _unittest_toolchain_impl(ctx):
+    return [
+        platform_common.ToolchainInfo(
+            unittest_toolchain_info = _UnittestToolchain(
+                file_ext = ctx.attr.file_ext,
+                success_templ = ctx.attr.success_templ,
+                failure_templ = ctx.attr.failure_templ,
+                join_on = ctx.attr.join_on,
+            ),
+        ),
+    ]
+
+unittest_toolchain = rule(
+    implementation = _unittest_toolchain_impl,
+    attrs = {
+        "file_ext": attr.string(mandatory = True),
+        "success_templ": attr.string(mandatory = True),
+        "failure_templ": attr.string(mandatory = True),
+        "join_on": attr.string(mandatory = True),
+    },
+)
+
 def _make(impl, attrs = None):
     """Creates a unit test rule from its implementation function.
 
@@ -41,7 +78,7 @@ def _make(impl, attrs = None):
 
       # Assert statements go here
 
-      unittest.end(env)
+      return unittest.end(env)
 
     your_test = unittest.make(_your_test)
     ```
@@ -75,6 +112,7 @@ def _make(impl, attrs = None):
         attrs = attrs,
         _skylark_testable = True,
         test = True,
+        toolchains = [TOOLCHAIN_TYPE],
     )
 
 def _suite(name, *test_rules):
@@ -160,17 +198,20 @@ def _end(env):
     Args:
       env: The test environment returned by `unittest.begin`.
     """
-    cmd = "\n".join([
-        "cat << EOF",
-        "\n".join(env.failures),
-        "EOF",
-        "exit %d" % len(env.failures),
-    ])
+
+    tc = env.ctx.toolchains[TOOLCHAIN_TYPE].unittest_toolchain_info
+    testbin = env.ctx.actions.declare_file(env.ctx.label.name + tc.file_ext)
+    if env.failures:
+        cmd = tc.failure_templ % tc.join_on.join(env.failures)
+    else:
+        cmd = tc.success_templ
+
     env.ctx.actions.write(
-        output = env.ctx.outputs.executable,
+        output = testbin,
         content = cmd,
         is_executable = True,
     )
+    return [DefaultInfo(executable = testbin)]
 
 def _fail(env, msg):
     """Unconditionally causes the current test to fail.
diff --git a/tests/collections_tests.bzl b/tests/collections_tests.bzl
index 27f6d97..9e86672 100644
--- a/tests/collections_tests.bzl
+++ b/tests/collections_tests.bzl
@@ -37,7 +37,7 @@ def _after_each_test(ctx):
         collections.after_each(None, ["a", "b"]),
     )
 
-    unittest.end(env)
+    return unittest.end(env)
 
 after_each_test = unittest.make(_after_each_test)
 
@@ -61,7 +61,7 @@ def _before_each_test(ctx):
         collections.before_each(None, ["a", "b"]),
     )
 
-    unittest.end(env)
+    return unittest.end(env)
 
 before_each_test = unittest.make(_before_each_test)
 
@@ -99,7 +99,7 @@ def _uniq_test(ctx):
         ],
     )
 
-    unittest.end(env)
+    return unittest.end(env)
 
 uniq_test = unittest.make(_uniq_test)
 
diff --git a/tests/dicts_tests.bzl b/tests/dicts_tests.bzl
index 99bdaac..5835323 100644
--- a/tests/dicts_tests.bzl
+++ b/tests/dicts_tests.bzl
@@ -63,7 +63,7 @@ def _add_test(ctx):
     result["a"] = 2
     asserts.equals(env, 1, original["a"])
 
-    unittest.end(env)
+    return unittest.end(env)
 
 add_test = unittest.make(_add_test)
 
diff --git a/tests/new_sets_tests.bzl b/tests/new_sets_tests.bzl
index c3d6ae2..e73b7d4 100644
--- a/tests/new_sets_tests.bzl
+++ b/tests/new_sets_tests.bzl
@@ -36,7 +36,7 @@ def _is_equal_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.true(env, sets.is_equal(sets.make([1, 1]), sets.make([1])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_equal_test = unittest.make(_is_equal_test)
 
@@ -54,7 +54,7 @@ def _is_subset_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.true(env, sets.is_subset(sets.make([1, 1]), sets.make([1, 2])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_subset_test = unittest.make(_is_subset_test)
 
@@ -72,7 +72,7 @@ def _disjoint_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.false(env, sets.disjoint(sets.make([1, 1]), sets.make([1, 2])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 disjoint_test = unittest.make(_disjoint_test)
 
@@ -90,7 +90,7 @@ def _intersection_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.new_set_equals(env, sets.make([1]), sets.intersection(sets.make([1, 1]), sets.make([1, 2])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 intersection_test = unittest.make(_intersection_test)
 
@@ -110,7 +110,7 @@ def _union_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.new_set_equals(env, sets.make([1, 2]), sets.union(sets.make([1, 1]), sets.make([1, 2])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 union_test = unittest.make(_union_test)
 
@@ -128,7 +128,7 @@ def _difference_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.new_set_equals(env, sets.make([2]), sets.difference(sets.make([1, 2]), sets.make([1, 1])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 difference_test = unittest.make(_difference_test)
 
@@ -140,7 +140,7 @@ def _to_list_test(ctx):
     asserts.equals(env, [1], sets.to_list(sets.make([1, 1, 1])))
     asserts.equals(env, [1, 2, 3], sets.to_list(sets.make([1, 2, 3])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 to_list_test = unittest.make(_to_list_test)
 
@@ -151,7 +151,7 @@ def _make_test(ctx):
     asserts.equals(env, {}, sets.make()._values)
     asserts.equals(env, {x: None for x in [1, 2, 3]}, sets.make([1, 1, 2, 2, 3, 3])._values)
 
-    unittest.end(env)
+    return unittest.end(env)
 
 make_test = unittest.make(_make_test)
 
@@ -168,7 +168,7 @@ def _copy_test(ctx):
     copy._values[5] = None
     asserts.false(env, sets.is_equal(original, copy))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 copy_test = unittest.make(_copy_test)
 
@@ -188,7 +188,7 @@ def _insert_test(ctx):
         msg = "Insert creates a new set which is an O(n) operation, insert should be O(1).",
     )
 
-    unittest.end(env)
+    return unittest.end(env)
 
 insert_test = unittest.make(_insert_test)
 
@@ -201,7 +201,7 @@ def _contains_test(ctx):
     asserts.true(env, sets.contains(sets.make([1, 2]), 1))
     asserts.false(env, sets.contains(sets.make([2, 3]), 1))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 contains_test = unittest.make(_contains_test)
 
@@ -213,7 +213,7 @@ def _length_test(ctx):
     asserts.equals(env, 1, sets.length(sets.make([1])))
     asserts.equals(env, 2, sets.length(sets.make([1, 2])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 length_test = unittest.make(_length_test)
 
@@ -228,7 +228,7 @@ def _remove_test(ctx):
     after_removal = sets.remove(original, 3)
     asserts.new_set_equals(env, original, after_removal)
 
-    unittest.end(env)
+    return unittest.end(env)
 
 remove_test = unittest.make(_remove_test)
 
@@ -244,7 +244,7 @@ def _repr_str_test(ctx):
     asserts.equals(env, "[1]", sets.str(sets.make([1])))
     asserts.equals(env, "[1, 2]", sets.str(sets.make([1, 2])))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 repr_str_test = unittest.make(_repr_str_test)
 
diff --git a/tests/partial_tests.bzl b/tests/partial_tests.bzl
index 94732ee..6d778c3 100644
--- a/tests/partial_tests.bzl
+++ b/tests/partial_tests.bzl
@@ -72,7 +72,7 @@ def _make_call_test(ctx):
     foo = partial.make(_call_args_kwargs, 100, func_mult = 10)
     asserts.equals(env, 1120, partial.call(foo, 12, func_mult = 5, call_mult = 2))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 make_call_test = unittest.make(_make_call_test)
 
diff --git a/tests/paths_tests.bzl b/tests/paths_tests.bzl
index bac95e1..aaf3e3e 100644
--- a/tests/paths_tests.bzl
+++ b/tests/paths_tests.bzl
@@ -37,7 +37,7 @@ def _basename_test(ctx):
     asserts.equals(env, "", paths.basename("foo/"))
     asserts.equals(env, "", paths.basename("/foo/"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 basename_test = unittest.make(_basename_test)
 
@@ -62,7 +62,7 @@ def _dirname_test(ctx):
     asserts.equals(env, "foo", paths.dirname("foo/"))
     asserts.equals(env, "/foo", paths.dirname("/foo/"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 dirname_test = unittest.make(_dirname_test)
 
@@ -84,7 +84,7 @@ def _is_absolute_test(ctx):
     asserts.true(env, paths.is_absolute("/foo/"))
     asserts.true(env, paths.is_absolute("/foo/bar"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_absolute_test = unittest.make(_is_absolute_test)
 
@@ -128,7 +128,7 @@ def _join_test(ctx):
     asserts.equals(env, "foo", paths.join("", "", "foo"))
     asserts.equals(env, "foo/bar", paths.join("foo", "", "", "bar"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 join_test = unittest.make(_join_test)
 
@@ -170,7 +170,7 @@ def _normalize_test(ctx):
     asserts.equals(env, "foo", paths.normalize("foo/"))
     asserts.equals(env, "foo/bar", paths.normalize("foo/bar/"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 normalize_test = unittest.make(_normalize_test)
 
@@ -196,7 +196,7 @@ def _relativize_test(ctx):
 
     # TODO(allevato): Test failure cases, once that is possible.
 
-    unittest.end(env)
+    return unittest.end(env)
 
 relativize_test = unittest.make(_relativize_test)
 
@@ -227,7 +227,7 @@ def _replace_extension_test(ctx):
     # Verify that we don't insert a period on the extension if none is provided.
     asserts.equals(env, "foobaz", paths.replace_extension("foo.bar", "baz"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 replace_extension_test = unittest.make(_replace_extension_test)
 
@@ -266,7 +266,7 @@ def _split_extension_test(ctx):
     asserts.equals(env, (".a/b", ".c"), paths.split_extension(".a/b.c"))
     asserts.equals(env, (".a", ".b"), paths.split_extension(".a.b"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 split_extension_test = unittest.make(_split_extension_test)
 
diff --git a/tests/selects_tests.bzl b/tests/selects_tests.bzl
index 94987cb..87a6d3b 100644
--- a/tests/selects_tests.bzl
+++ b/tests/selects_tests.bzl
@@ -53,7 +53,7 @@ def _with_or_test(ctx):
         selects.with_or_dict(mixed_dict),
     )
 
-    unittest.end(env)
+    return unittest.end(env)
 
 with_or_test = unittest.make(_with_or_test)
 
diff --git a/tests/sets_tests.bzl b/tests/sets_tests.bzl
index 7f84260..f7d99bb 100644
--- a/tests/sets_tests.bzl
+++ b/tests/sets_tests.bzl
@@ -39,7 +39,7 @@ def _is_equal_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.true(env, sets.is_equal([1, 1], [1]))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_equal_test = unittest.make(_is_equal_test)
 
@@ -58,7 +58,7 @@ def _is_subset_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.true(env, sets.is_subset([1, 1], [1, 2]))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_subset_test = unittest.make(_is_subset_test)
 
@@ -77,7 +77,7 @@ def _disjoint_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.false(env, sets.disjoint([1, 1], [1, 2]))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 disjoint_test = unittest.make(_disjoint_test)
 
@@ -96,7 +96,7 @@ def _intersection_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.set_equals(env, [1], sets.intersection([1, 1], [1, 2]))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 intersection_test = unittest.make(_intersection_test)
 
@@ -117,7 +117,7 @@ def _union_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.set_equals(env, [1, 2], sets.union([1, 1], [1, 2]))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 union_test = unittest.make(_union_test)
 
@@ -136,7 +136,7 @@ def _difference_test(ctx):
     # If passing a list, verify that duplicate elements are ignored.
     asserts.set_equals(env, [2], sets.difference([1, 2], [1, 1]))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 difference_test = unittest.make(_difference_test)
 
diff --git a/tests/shell_tests.bzl b/tests/shell_tests.bzl
index f706191..dffe03d 100644
--- a/tests/shell_tests.bzl
+++ b/tests/shell_tests.bzl
@@ -27,7 +27,7 @@ def _shell_array_literal_test(ctx):
     asserts.equals(env, "('$foo')", shell.array_literal(["$foo"]))
     asserts.equals(env, "('qu\"o\"te')", shell.array_literal(['qu"o"te']))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 shell_array_literal_test = unittest.make(_shell_array_literal_test)
 
@@ -48,7 +48,7 @@ def _shell_quote_test(ctx):
     asserts.equals(env, "'foo\\bar'", shell.quote("foo\\bar"))
     asserts.equals(env, "'back`echo q`uote'", shell.quote("back`echo q`uote"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 shell_quote_test = unittest.make(_shell_quote_test)
 
diff --git a/tests/structs_tests.bzl b/tests/structs_tests.bzl
index 3f66860..79de7ad 100644
--- a/tests/structs_tests.bzl
+++ b/tests/structs_tests.bzl
@@ -42,7 +42,7 @@ def _add_test(ctx):
         structs.to_dict(struct(a = 1, b = struct(bb = 1))),
     )
 
-    unittest.end(env)
+    return unittest.end(env)
 
 add_test = unittest.make(_add_test)
 
diff --git a/tests/types_tests.bzl b/tests/types_tests.bzl
index 1fd5dba..55cc64e 100644
--- a/tests/types_tests.bzl
+++ b/tests/types_tests.bzl
@@ -36,7 +36,7 @@ def _is_string_test(ctx):
     asserts.false(env, types.is_string(None))
     asserts.false(env, types.is_string(_a_function))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_string_test = unittest.make(_is_string_test)
 
@@ -56,7 +56,7 @@ def _is_bool_test(ctx):
     asserts.false(env, types.is_bool(None))
     asserts.false(env, types.is_bool(_a_function))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_bool_test = unittest.make(_is_bool_test)
 
@@ -76,7 +76,7 @@ def _is_list_test(ctx):
     asserts.false(env, types.is_list(None))
     asserts.false(env, types.is_list(_a_function))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_list_test = unittest.make(_is_list_test)
 
@@ -96,7 +96,7 @@ def _is_none_test(ctx):
     asserts.false(env, types.is_none([1]))
     asserts.false(env, types.is_none(_a_function))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_none_test = unittest.make(_is_none_test)
 
@@ -117,7 +117,7 @@ def _is_int_test(ctx):
     asserts.false(env, types.is_int(None))
     asserts.false(env, types.is_int(_a_function))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_int_test = unittest.make(_is_int_test)
 
@@ -138,7 +138,7 @@ def _is_tuple_test(ctx):
     asserts.false(env, types.is_tuple(None))
     asserts.false(env, types.is_tuple(_a_function))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_tuple_test = unittest.make(_is_tuple_test)
 
@@ -159,7 +159,7 @@ def _is_dict_test(ctx):
     asserts.false(env, types.is_dict(None))
     asserts.false(env, types.is_dict(_a_function))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_dict_test = unittest.make(_is_dict_test)
 
@@ -179,7 +179,7 @@ def _is_function_test(ctx):
     asserts.false(env, types.is_function([1]))
     asserts.false(env, types.is_function(None))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 is_function_test = unittest.make(_is_function_test)
 
diff --git a/tests/versions_tests.bzl b/tests/versions_tests.bzl
index f4b1a38..422cb41 100644
--- a/tests/versions_tests.bzl
+++ b/tests/versions_tests.bzl
@@ -26,7 +26,7 @@ def _parse_test(ctx):
     asserts.equals(env, (0, 4, 0), versions.parse("0.4.0"))
     asserts.equals(env, (0, 4, 0), versions.parse("0.4.0rc"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 def _version_comparison_test(ctx):
     """Unit tests for versions.is_at_least and is_at_most"""
@@ -42,7 +42,7 @@ def _version_comparison_test(ctx):
     asserts.true(env, versions.is_at_most("0.4.0", "0.4.0rc3"))
     asserts.true(env, versions.is_at_most("1.4.0", "0.4.0rc3"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 def _check_test(ctx):
     """Unit tests for versions.check"""
@@ -53,7 +53,7 @@ def _check_test(ctx):
     asserts.equals(env, None, versions.check("0.4.5", bazel_version = "0.10.0rc1 abcd123"))
     asserts.equals(env, None, versions.check("0.4.5", maximum_bazel_version = "1.0.0", bazel_version = "0.10.0rc1 abcd123"))
 
-    unittest.end(env)
+    return unittest.end(env)
 
 parse_test = unittest.make(_parse_test)
 version_comparison_test = unittest.make(_version_comparison_test)
diff --git a/toolchains/unittest/BUILD b/toolchains/unittest/BUILD
new file mode 100644
index 0000000..195bbb6
--- /dev/null
+++ b/toolchains/unittest/BUILD
@@ -0,0 +1,47 @@
+load("//lib:unittest.bzl", "TOOLCHAIN_TYPE", "unittest_toolchain")
+
+toolchain_type(
+    name = "toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+unittest_toolchain(
+    name = "cmd",
+    failure_templ = """@echo off
+echo %s
+exit /b 1
+""",
+    file_ext = ".bat",
+    join_on = "\necho ",
+    success_templ = "@exit /b 0",
+    visibility = ["//visibility:public"],
+)
+
+unittest_toolchain(
+    name = "bash",
+    failure_templ = """#!/bin/sh
+cat <<'EOF'
+%s
+EOF
+exit 1
+""",
+    file_ext = ".sh",
+    join_on = "\n",
+    success_templ = "#!/bin/sh\nexit 0",
+    visibility = ["//visibility:public"],
+)
+
+toolchain(
+    name = "cmd_toolchain",
+    exec_compatible_with = [
+        "@bazel_tools//platforms:windows",
+    ],
+    toolchain = ":cmd",
+    toolchain_type = TOOLCHAIN_TYPE,
+)
+
+toolchain(
+    name = "bash_toolchain",
+    toolchain = ":bash",
+    toolchain_type = TOOLCHAIN_TYPE,
+)
diff --git a/workspace.bzl b/workspace.bzl
new file mode 100644
index 0000000..50b6db5
--- /dev/null
+++ b/workspace.bzl
@@ -0,0 +1,5 @@
+load("@bazel_skylib//lib:unittest.bzl", "register_unittest_toolchains")
+
+def bazel_skylib_workspace():
+    """Registers toolchains and declares repository dependencies of the bazel_skylib repository."""
+    register_unittest_toolchains()