feat: add test_suite containing all tests from write_source_files (#256)

lib/private/write_source_file.bzl

@@ -30,6 +30,9 @@ def write_source_file(
         suggested_update_target: Label of the write_source_file target to suggest running when files are out of date
         diff_test: Generate a test target to check that the source file(s) exist and are up to date with the generated files(s).
         **kwargs: Other common named parameters such as `tags` or `visibility`
+
+    Returns:
+        Name of the generated test target if requested, otherwise None.
     """
     if out_file:
         if not in_file:
@@ -59,7 +62,7 @@ def write_source_file(
     )
 
     if not in_file or not out_file or not diff_test:
-        return
+        return None
 
     out_file_missing = _is_file_missing(out_file)
     test_target_name = "%s_test" % name
@@ -126,6 +129,8 @@ To update *only* this file, run:
             **kwargs
         )
 
+    return test_target_name
+
 _write_source_file_attrs = {
     "in_file": attr.label(allow_files = True, mandatory = False),
     # out_file is intentionally an attr.string() and not a attr.label(). This is so that

lib/write_source_files.bzl

@@ -95,6 +95,7 @@ def write_source_files(
 
     single_update_target = len(files.keys()) == 1
     update_targets = []
+    test_targets = []
     for i, pair in enumerate(files.items()):
         out_file, in_file = pair
 
@@ -108,7 +109,7 @@ def write_source_files(
                 this_suggested_update_target = name
 
         # Runnable target that writes to the out file to the source tree
-        _write_source_file(
+        test_target = _write_source_file(
             name = update_target_name,
             in_file = in_file,
             out_file = out_file,
@@ -118,6 +119,17 @@ def write_source_files(
             **kwargs
         )
 
+        if test_target:
+            test_targets.append(test_target)
+
+    if len(test_targets) > 0:
+        native.test_suite(
+            name = "%s_tests" % name,
+            tests = test_targets,
+            visibility = kwargs.get("visibility"),
+            tags = kwargs.get("tags"),
+        )
+
     if not single_update_target:
         _write_source_file(
             name = name,