1 files changed, 61 insertions, 0 deletions
diff --git a/tests/test_context.py b/tests/test_context.py
index ad010a37..919286c5 100644
--- a/tests/test_context.py
+++ b/tests/test_context.py
@@ -6,7 +6,9 @@
 import os.path
 
 import coverage
+from coverage import env
 from coverage.data import CoverageData
+from coverage.misc import CoverageException
 
 from tests.coveragetest import CoverageTest
 
@@ -102,3 +104,62 @@ class StaticContextTest(CoverageTest):
             self.assertEqual(combined.arcs(fred, context='blue'), [])
             self.assertEqual(combined.arcs(fblue, context='red'), [])
             self.assertEqual(combined.arcs(fblue, context='blue'), self.ARCS)
+
+
+class DynamicContextTest(CoverageTest):
+    """Tests of dynamically changing contexts."""
+
+    def setUp(self):
+        super(DynamicContextTest, self).setUp()
+        self.skip_unless_data_storage_is("sql")
+        if not env.C_TRACER:
+            self.skipTest("Only the C tracer supports dynamic contexts")
+
+    def test_simple(self):
+        self.make_file("two_tests.py", """\
+            def helper(lineno):
+                x = 2
+
+            def test_one():
+                a = 5
+                helper(6)
+
+            def test_two():
+                a = 9
+                b = 10
+                if a > 11:
+                    b = 12
+                assert a == (13-4)
+                assert b == (14-4)
+                helper(15)
+
+            test_one()
+            x = 18
+            helper(19)
+            test_two()
+            """)
+        cov = coverage.Coverage(source=["."])
+        cov.set_option("run:dynamic_context", "test_function")
+        self.start_import_stop(cov, "two_tests")
+        data = cov.get_data()
+
+        fname = os.path.abspath("two_tests.py")
+        self.assertCountEqual(data.measured_contexts(), ["", "test_one", "test_two"])
+        self.assertCountEqual(data.lines(fname, ""), [1, 4, 8, 17, 18, 19, 2, 20])
+        self.assertCountEqual(data.lines(fname, "test_one"), [5, 6, 2])
+        self.assertCountEqual(data.lines(fname, "test_two"), [9, 10, 11, 13, 14, 15, 2])
+
+
+class DynamicContextWithPythonTracerTest(CoverageTest):
+    """The Python tracer doesn't do dynamic contexts at all."""
+
+    run_in_temp_dir = False
+
+    def test_python_tracer_fails_properly(self):
+        if env.C_TRACER:
+            self.skipTest("This test is specifically about the Python tracer.")
+        cov = coverage.Coverage()
+        cov.set_option("run:dynamic_context", "test_function")
+        msg = r"Can't support dynamic contexts with PyTracer"
+        with self.assertRaisesRegex(CoverageException, msg):
+            cov.start()