SERVER-34798 Remove ServiceContext subclasses and use new ServiceContext in every unit test.

This patch does several loosely related and surprisingly hard to separate things.

1.) Make the ServiceContext class final

2.) Create a mechanism, called ConstructorActions, for running methods on
ServiceContexts immediately after they're built and immediately before they're
destroyed.

3.) Introduce / improve test fixture base classes for tests, giving them fresh
ServiceContext instances for each test case. There is one fixture for tests that
need a storage engine and another for those that do not.

4.) Make several remaining global variables SC decorations in support of (3)

5.) Replace many MONGO_INITIALIZERS that access getGlobalServiceContext with the
new constructor-actions system, which is needed for (3.)

6.) Fix up tests to use the fixtures from (3) and fix tests that silently used
different service contexts in together in a technically illegal fashion that now
breaks.

7.) Utilize (2) as necessary to simplify initialization of new ServiceContexts,
simplifying the fixtures in (3).

1 files changed, 4 insertions, 18 deletions

diff --git a/src/mongo/db/service_context_devnull_test_fixture.h b/src/mongo/db/service_context_devnull_test_fixture.h
index 77a0d551965..1304546f903 100644
--- a/src/mongo/db/service_context_devnull_test_fixture.h
+++ b/src/mongo/db/service_context_devnull_test_fixture.h
@@ -28,30 +28,16 @@
 
 #pragma once
 
-#include "mongo/unittest/unittest.h"
+#include "mongo/db/service_context_d_test_fixture.h"
 
 namespace mongo {
 
-class ServiceContext;
-
 /**
  * Test fixture class for mongod tests that use the "devnull" storage engine.
  */
-class ServiceContextDevnullTestFixture : public unittest::Test {
-public:
-    /**
-     * Initializes the devnull engine as the global storage engine.
-     * Also sets up a Client on the thread, which can be accessed via 'cc()'.
-     */
-    void setUp() override;
-
-    void tearDown() override;
-
-    /**
-     * Returns a service context, which is only valid for this instance of the test.
-     * Must not be called before setUp() or after tearDown().
-     */
-    ServiceContext* getServiceContext();
+class ServiceContextDevnullTestFixture : public ServiceContextMongoDTest {
+protected:
+    ServiceContextDevnullTestFixture();
 };
 
 }  // namespace mongo