delete all users at the start of each test. (#129)

internal/iam/repository_user_test.go

@@ -515,6 +515,7 @@ func TestRepository_ListUsers(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			assert, require := assert.New(t), require.New(t)
+			require.NoError(conn.Where("1=1").Delete(allocUser()).Error)
 			testUsers := []*User{}
 			for i := 0; i < tt.createCnt; i++ {
 				testUsers = append(testUsers, TestUser(t, conn, org.PublicId))