Add subworkflow test

Author: LouisLeNezet

tests/pipelines/lint/test_subworkflows_json.py

@@ -0,0 +1,10 @@
+from ..test_lint import TestLint
+
+
+class TestLintSubworkflowsJson(TestLint):
+    def test_subworkflows_json_pass(self):
+        self.lint_obj._load()
+        results = self.lint_obj.subworkflows_json()
+        assert len(results.get("warned", [])) == 0
+        assert len(results.get("failed", [])) == 0
+        assert len(results.get("passed", [])) > 0