cleanup(tests): Use new APIs in rules_testing 0.4.0 (#1307)

* Use public APIs for DictSubject and StrSubject.
* Use rules_testing's StructSubject instead of our own.

Work towards 1297

tests/cc/py_cc_toolchain/py_cc_toolchain_tests.bzl

@@ -44,15 +44,10 @@ def _py_cc_toolchain_test_impl(env, target):
     )
     toolchain.python_version().equals("3.999")
 
-    toolchain_headers = toolchain.headers()
-    toolchain_headers.providers_map().keys().contains_exactly(["CcInfo", "DefaultInfo"])
+    headers_providers = toolchain.headers().providers_map()
+    headers_providers.keys().contains_exactly(["CcInfo", "DefaultInfo"])
 
-    cc_info = cc_info_subject(
-        # TODO: Use DictSubject.get once available,
-        # https://github.com/bazelbuild/rules_testing/issues/51
-        toolchain_headers.actual.providers_map["CcInfo"],
-        meta = env.expect.meta.derive(expr = "cc_info"),
-    )
+    cc_info = headers_providers.get("CcInfo", factory = cc_info_subject)
 
     compilation_context = cc_info.compilation_context()
     compilation_context.direct_headers().contains_exactly([
@@ -68,8 +63,11 @@ def _py_cc_toolchain_test_impl(env, target):
         matching.str_matches("*/fake_include"),
     ])
 
+    # TODO: Once subjects.default_info is available, do
+    # default_info = headers_providers.get("DefaultInfo", factory=subjects.default_info)
+    # https://github.com/bazelbuild/rules_python/issues/1297
     default_info = default_info_subject(
-        toolchain_headers.actual.providers_map["DefaultInfo"],
+        headers_providers.get("DefaultInfo", factory = lambda v, meta: v),
         meta = env.expect.meta.derive(expr = "default_info"),
     )
     default_info.runfiles().contains_predicate(

tests/py_cc_toolchain_info_subject.bzl

@@ -13,14 +13,7 @@
 # limitations under the License.
 """PyCcToolchainInfo testing subject."""
 
-# TODO: Load this through truth.bzl#subjects when made available
-# https://github.com/bazelbuild/rules_testing/issues/54
-load("@rules_testing//lib/private:dict_subject.bzl", "DictSubject")  # buildifier: disable=bzl-visibility
-
-# TODO: Load this through truth.bzl#subjects when made available
-# https://github.com/bazelbuild/rules_testing/issues/54
-load("@rules_testing//lib/private:str_subject.bzl", "StrSubject")  # buildifier: disable=bzl-visibility
-load(":struct_subject.bzl", "struct_subject")
+load("@rules_testing//lib:truth.bzl", "subjects")
 
 def _py_cc_toolchain_info_subject_new(info, *, meta):
     # buildifier: disable=uninitialized
@@ -33,14 +26,16 @@ def _py_cc_toolchain_info_subject_new(info, *, meta):
     return public
 
 def _py_cc_toolchain_info_subject_headers(self):
-    return struct_subject(
+    return subjects.struct(
         self.actual.headers,
         meta = self.meta.derive("headers()"),
-        providers_map = DictSubject.new,
+        attrs = dict(
+            providers_map = subjects.dict,
+        ),
     )
 
 def _py_cc_toolchain_info_subject_python_version(self):
-    return StrSubject.new(
+    return subjects.str(
         self.actual.python_version,
         meta = self.meta.derive("python_version()"),
     )