Add coverage

tools/telemetry/third_party/coverage/tests/test_collector.py

Index: tools/telemetry/third_party/coverage/tests/test_collector.py
diff --git a/tools/telemetry/third_party/coverage/tests/test_collector.py b/tools/telemetry/third_party/coverage/tests/test_collector.py
new file mode 100644
index 0000000000000000000000000000000000000000..bd96341588b3881d755a92f96176358de80bc3fc
--- /dev/null
+++ b/tools/telemetry/third_party/coverage/tests/test_collector.py
@@ -0,0 +1,50 @@
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://bitbucket.org/ned/coveragepy/src/default/NOTICE.txt
+
+"""Tests of coverage/collector.py and other collectors."""
+
+import os.path
+
+import coverage
+
+from tests.coveragetest import CoverageTest
+from tests.helpers import CheckUniqueFilenames
+
+
+class CollectorTest(CoverageTest):
+    """Test specific aspects of the collection process."""
+
+    def test_should_trace_cache(self):
+        # The tracers should only invoke should_trace once for each file name.
+
+        # Make some files that invoke each other.
+        self.make_file("f1.py", """\
+            def f1(x, f):
+                return f(x)
+            """)
+
+        self.make_file("f2.py", """\
+            import f1
+
+            def func(x):
+                return f1.f1(x, otherfunc)
+
+            def otherfunc(x):
+                return x*x
+
+            for i in range(10):
+                func(i)
+            """)
+
+        # Trace one file, but not the other. CheckUniqueFilenames will assert
+        # that _should_trace hasn't been called twice for the same file.
+        cov = coverage.Coverage(include=["f1.py"])
+        should_trace_hook = CheckUniqueFilenames.hook(cov, '_should_trace')
+
+        # Import the Python file, executing it.
+        self.start_import_stop(cov, "f2")
+
+        # Double-check that our files were checked.
+        abs_files = set(os.path.abspath(f) for f in should_trace_hook.filenames)
+        self.assertIn(os.path.abspath("f1.py"), abs_files)
+        self.assertIn(os.path.abspath("f2.py"), abs_files)