Fix test discovery unit tests.

Author: ericsnowcurrently

src/test/testing/common/services/discovery.unit.test.ts

@@ -77,15 +77,15 @@ suite('Unit Tests - Common Discovery', () => {
         };
 
         when(executionFactory.createActivatedEnvironment(deepEqual(creationOptions))).thenResolve(execService.object);
-        const executionResult = { stdout: discoveredTests };
+        const executionResult = { stdout: JSON.stringify(discoveredTests) };
         execService
             .setup((e) => e.exec(typemoq.It.isValue([pythonFile, ...options.args]), typemoq.It.isValue(spawnOptions)))
             .returns(() => Promise.resolve(executionResult));
 
         const result = await discovery.exec(options);
 
         execService.verifyAll();
-        assert.deepEqual(result, executionResult);
+        assert.deepEqual(result, discoveredTests);
     });
 });