measured_contexts() and two simple tests of the global context

4 files changed, 53 insertions, 13 deletions

diff --git a/coverage/data.py b/coverage/data.py
index 3250196d..3a2432b3 100644
--- a/coverage/data.py
+++ b/coverage/data.py
@@ -445,6 +445,11 @@ class CoverageJsonData(object):
 
         self._validate()
 
+    def set_context(self, context):
+        """Set the context. Not implemented for JSON storage."""
+        if context:
+            raise CoverageException("JSON storage doesn't support contexts")
+
     def write(self):
         """Write the collected coverage data to a file.
 
diff --git a/coverage/sqldata.py b/coverage/sqldata.py
index b9488557..45c1570c 100644
--- a/coverage/sqldata.py
+++ b/coverage/sqldata.py
@@ -179,18 +179,16 @@ class CoverageSqliteData(SimpleRepr):
         return self._file_map.get(filename)
 
     def set_context(self, context):
-        """Get the context id for `context`."""
+        """Set the current context for future `add_lines` etc."""
         self._start_using()
-        if not context:
-            self._context_id = 0
-        else:
-            with self._connect() as con:
-                row = con.execute("select id from context where context = ?", (context,)).fetchone()
-                if row is not None:
-                    self._context_id = row[0]
-                else:
-                    cur = con.execute("insert into context (context) values (?)", (context,))
-                    self._context_id = cur.lastrowid
+        context = context or ""
+        with self._connect() as con:
+            row = con.execute("select id from context where context = ?", (context,)).fetchone()
+            if row is not None:
+                self._context_id = row[0]
+            else:
+                cur = con.execute("insert into context (context) values (?)", (context,))
+                self._context_id = cur.lastrowid
 
     def add_lines(self, line_data):
         """Add measured line data.
@@ -384,6 +382,13 @@ class CoverageSqliteData(SimpleRepr):
         """A set of all files that had been measured."""
         return set(self._file_map)
 
+    def measured_contexts(self):
+        """A set of all contexts that have been measured."""
+        self._start_using()
+        with self._connect() as con:
+            contexts = set(row[0] for row in con.execute("select distinct(context) from context"))
+        return contexts
+
     def file_tracer(self, filename):
         """Get the plugin name of the file tracer for a file.
 
diff --git a/tests/test_context.py b/tests/test_context.py
new file mode 100644
index 00000000..ec1e4885
--- /dev/null
+++ b/tests/test_context.py
@@ -0,0 +1,30 @@
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
+
+"""Tests for context support."""
+
+import coverage
+
+from tests.coveragetest import CoverageTest
+
+
+class GlobalContextTest(CoverageTest):
+    """Tests of the global context."""
+
+    def setUp(self):
+        super(GlobalContextTest, self).setUp()
+        self.skip_unless_data_storage_is("sql")
+
+    def test_no_context(self):
+        self.make_file("main.py", "a = 1")
+        cov = coverage.Coverage()
+        self.start_import_stop(cov, "main")
+        data = cov.get_data()
+        self.assertCountEqual(data.measured_contexts(), [""])
+
+    def test_global_context(self):
+        self.make_file("main.py", "a = 1")
+        cov = coverage.Coverage(context="gooey")
+        self.start_import_stop(cov, "main")
+        data = cov.get_data()
+        self.assertCountEqual(data.measured_contexts(), ["gooey"])
diff --git a/tests/test_debug.py b/tests/test_debug.py
index 284d9567..63edc84f 100644
--- a/tests/test_debug.py
+++ b/tests/test_debug.py
@@ -144,8 +144,8 @@ class DebugTraceTest(CoverageTest):
             self.assertRegex(real_messages[-1], r"^\s*\d+\.\w{4}: Writing data")
             self.assertRegex(last_line, r"\s+_write_file : .*coverage[/\\]data.py @\d+$")
         else:
-            self.assertRegex(real_messages[-1], r"^\s*\d+\.\w{4}: Creating data file")
-            self.assertRegex(last_line, r"\s+_create_db : .*coverage[/\\]sqldata.py @\d+$")
+            self.assertRegex(real_messages[-1], r"^\s*\d+\.\w{4}: Adding lines")
+            self.assertRegex(last_line, r"\s+add_lines : .*coverage[/\\]sqldata.py @\d+$")
 
     def test_debug_config(self):
         out_lines = self.f1_debug_output(["config"])