This test requires a course with two teachers, two students, one graded assignment and a manually created grade item.
1) Access the course as teacher 1 and click on Course administration>Grades>Grader report
2) Grade student 1 in the manually created grade item.
3) Access the course as teacher 2 and go to the assignment grading screen. Grade the assignments of both students.
4) Access the grader report and give a manual grade to student 2. Edit the grade of student 1 (which teacher 1 added in step 2)
5) Log back in as teacher 1 and go to Course administration>Grades>Grade history.
6) Using the default history settings, verify you see all the changes made in steps 2-4
7) Change the grader to teacher 2 and verify you now see only the actions taken in steps 3 and 4
8) Change the grader to teacher 1 and verify you only see the actions taken in step 2
9) Click the Select users button, choosing first student 1 and then student 2, verifying you see the appropriate changes in steps 2-4
10) Select from the Grade item drop down the assignment and then the manual grade item and verify you see only the information about those items.